Unknown glitch in batch - batch-file

Question

I need help with an unknown issue in a recent batch file executed on Windows 10.
Proper function:
I am trying to make a math quiz which generates two numbers, a basic operand (+-x/), finds the answer, then checks it against an answer from a user. Additionally, the program is made to track certain information after a user has put in their answer. (Question number, the problem and answer, and the users response.)
My issue:
In certain scenarios the program will display the problem/answer in the "game" window rather than writing the problem/answer in the text file as intended.
The command is:
echo [Q]%m%>>"C:\Users\%username%\Desktop\%fname%.txt"
It is comment marked in the code below.
What I've done to fix the issue?
After testing for a descent while I discovered the issue seemed to revolve around the portion where it tries to move a problem/answer combo with division as the operation. This helped, but the issue started randomly popping up throughout future attempts to debug.
While I feel it is a bit frowned upon to ask two things at once I have two more issues.
Why does an operation like %a%%b%%c%=%d% (a,c,d being numbers and b being a /) break a certain command in my code consistently and how can I fix it?
Why does the same issue still randomly appear even if I erase all traces of division / which seems to cause my issue in the first place.
Here is the batch file:
::Initialization
#echo off
set /a prb=3
set file=Stat
set sss=s.
if %prb%==1 set tst=.
echo.
echo Welcome to math fire, you will get randomly generated
echo multiplication, addition, and subtraction problems. You
echo will go through a specified number before the game ends
echo and this window closes. You will be tracked in a file on
echo your desktop. You will have %prb% problem%sss%
echo.
pause
CLS
echo Get ready
timeout 5
set start=%time%
CLS
set /a num=1
set /a good=0
set /a bad=0
::===========================Set up beggining of stat file.
echo =-=-=-=-=-=>>"C:\Users\%username%\Desktop\%fname%.txt"
echo ===Start===>>"C:\Users\%username%\Desktop\%fname%.txt"
echo =-=-=-=-=-=>>"C:\Users\%username%\Desktop\%fname%.txt"
echo.>>"C:\Users\%username%\Desktop\%fname%.txt"
::===================================Main Body============
::[A] Num1 [B] Operator [C] Num2 [D] Answer [E] The problem [M] Problem and answer
:main
set /a a=%random% %% 30 + 1
::To remove the division section I changed the 4 below to 3
set /a b=%random% %% 4 + 1
set /a c=%random% %% 20 + 1
if %b%==1 set b=+
if %b%==2 set b=-
if %b%==3 set b=*
if %b%==4 set b=/
set /a d=%a%%b%%c%
set e=%a%%b%%c%
echo.
echo =============================%e%=?
echo.
timeout 1
set /p ans=+++++++++++++++++++++++++++++Answer:
set m=%e%=%d%
echo ===%num%===>>"C:\Users\%username%\Desktop\%fname%.txt"
::The following line is the glitching code
echo [Q]%m%>>"C:\Users\%username%\Desktop\%fname%.txt"
echo [A]%ans%>>"C:\Users\%username%\Desktop\%fname%.txt"
echo.>>"C:\Users\%username%\Desktop\%fname%.txt"
if %ans%==%d% goto p
CLS
echo.
echo -----------------------------Incorrect
set /a bad=%bad%+1
goto re
:p
CLS
echo.
echo -----------------------------Correct
set /a good=%good%+1
goto re
:re
if %num%==%prb% goto end
set /a num=%num%+1
goto main
:end
echo ===========>>"C:\Users\%username%\Desktop\%fname%.txt"
echo.>>"C:\Users\%username%\Desktop\%fname%.txt"
echo [Start]%start%>>"C:\Users\%username%\Desktop\%fname%.txt"
echo [-End-]%time%>>"C:\Users\%username%\Desktop\%fname%.txt"
echo [Right]%good%>>"C:\Users\%username%\Desktop\%fname%.txt"
echo [Wrong]%bad%>>"C:\Users\%username%\Desktop\%fname%.txt"
echo.>>"C:\Users\%username%\Desktop\%fname%.txt"
echo =-=-=-=-=-=>>"C:\Users\%username%\Desktop\%fname%.txt"
echo ===-End-===>>"C:\Users\%username%\Desktop\%fname%.txt"
echo =-=-=-=-=-=>>"C:\Users\%username%\Desktop\%fname%.txt"
echo.>>"C:\Users\%username%\Desktop\%fname%.txt"
CLS
echo.
echo.
echo.
echo Congrats, check your desktop for your play info.
echo.
echo.
echo.
pause
exit

Answer 1

Use the syntax
>>"%filename1%" echo [Q]%m%
(my testfiles are allotted in variables)
Noting that m will contain a string such as 13/14=0
The character just before a redirector redirects the logical device number. You can get around this by moving the redirction to the start of the command or inserting a space before the redirector or using
>>"%filename1%" (
echo [Q]%m%
echo something else
echo more text
)
or
(
echo [Q]%m%
echo something else
echo more text
)>>"%filename1%"
which does the same thing - gather the output of the echoes and redirect the sum-output to the file.
Oh, BTW - batch does integer mathematics, so 13/4=3 - no decimals.