# Checking correctness of algebraic answer

I cannot get the computational layer to check a simple algebraic expression in math input.

I want to check p/q

Hi Kevin,

if you want to check that the student wrote the ratio p/q you could use a simplefunction

correct: simpleFunction(this.latex,“p”,“q”).evaluateAt(1.2,8) = 0.15

technically they can also get this marked correct if they input 0.15, but the odds of them guessing that output to the function are incredibly remote

correct: simpleFunction(this.latex,“p”,“q”).evaluateAt(1.2,7) = numericValue(\frac{1.2}{7})

if you really want to make unlikely they guess the correct output, use a fraction with a repeating decimal as your checking output.