@Metahofzicht Nailed it. I found out how to fix it.

My grading code:

local I:=II:

if evalb(simplify(algsubs(I = a^4/(32*sqrt(3)), algsubs(C = 192, $RESPONSE) = $RV1))) then 1.0;

elif evalb(simplify(algsubs(I = a^4/(32*sqrt(3)), algsubs(C[1] = 192, $RESPONSE) = $RV1))) then 1.0;

elif algsubs($fact2 = 1,$RESPONSE) <> $RESPONSE then 1.0;

else 0.0;

end if;

Custom previewing code: local I:=`I `:printf(MathML[ExportPresentation]($RESPONSE));

my algoritm:

$fact2 = "E*a^4/L^3";

$RV1 = "$fact2*2*sqrt(3)";

$RVdisplay = "printf(MathML[ExportPresentation]($RV1))";