# Numeric vs Latex Issue

Here is my problem:

I created two variables a and b and want to add, subtract, multiply them and have CL check for correctness. I think have to do this in the graphing calculator. But I want students to have to input using latex (otherwise they will just put in the expression!)

So if I create a variable c in the graphing calculator how do I covert that number to latex so I can check when a student puts it in math type (expression)?

Hope that makes sense!

If you want to check that a specific number is used, you need to use countNumberUsage:

``````a=2
b=6
sum=numericValue("\${a}+\${b}")
c=input.latex
check= input.numericValue=sum and countNumberUsage(c,sum)=1
and countNumberUsage(c)=1
correct: check
``````

â€ścheckâ€ť is first checking if the student answer evaluates to â€śsumâ€ť, then checks if the actual number â€śsumâ€ť occurs in the answer once. Last, itâ€™s checking there is only one number total being used, which may make the second check redundant, but itâ€™s useful in many other cases like checking for expressions with more than one term.

1 Like

Thank you so much, Daniel!

Fixed a problem andâ€¦ best of all, learned some new tricks!