@Echo Off
more/c<nul
call :_calc sub "12.72-8.189605-1.0025" "adt"
call :_calc add "%adt%+521.27+5" "adt"
echo: 12.72 - 8.189605 - 1.0025 + 521.27 + 5 = %adt%
pause 1>nul
exit
:_calc
setlocal enabledelayedexpansion
if "%~1" EQU "add" set "sym=+"
if "%~1" EQU "sub" set "sym=-"
set "add_str=%~2"
set "add_str=!add_str:%sym%= !"
set/a hst=0,cnt=0,add=0
for %%_ in (%add_str%) do (
	set/a dec[!cnt!]=0
	for /f "tokens=2 delims=." %%. in ("%%_") do (
		call :_strlen "%%."
		set/a dec[!cnt!]=!errorlevel!
		if !errorlevel! GTR !hst! set/a hst=!errorlevel!
	)
	set/a cnt+=1
)
set/a cnt=0
if "%sym%" EQU "-" for %%_ in (%add_str:.=%) do (
	set/a pow=%hst%-%dec[0]%,n_b=%%_
	for /l %%. in (1,1,!pow!) do set "n_b=!n_b!0"
	set/a add+=!n_b!*2
	goto :__op
)
:__op
for %%_ in (%add_str:.=%) do (
	call set/a pow=%hst%-%%dec[!cnt!]%%,n_b=%%_
	for /l %%. in (1,1,!pow!) do set "n_b=!n_b!0"
	set/a add%sym%=!n_b!,cnt+=1
)
set "res=!add:~0,-%hst%!.!add:~-%hst%!"
if %hst% EQU 0 set "res=%res:~1%"
endlocal & set "%~3=%res%" & exit /b
:_strlen
	setlocal
	set/a cnt=0
	for /f "tokens=* eol=" %%_ in (
		'"cmd /u /c echo:%~1|more"'
	) do set/a cnt+=1
	endlocal & exit /b %cnt%

call :_calc add|sub "operación" "variable"

echo. %variable%

@echo off
echo ingrese primer numero
set  /p "a="
echo ingrese segundo numero
set /p "b="
call :_calc sub "%a%-%b%" "adt"
echo. Resultado de la resta: %adt%
pause > nul
exit