To find the factor coefficient variable, you would divide the numbers by a number that could be divisible for both numbers. In the case, the number you going to be dividing with is 5.
When you divide, your equation would look like this:
[tex]\frac{5c-15}{5}[/tex]
When you divide the numbers by 5, you would end of up with 5(c-3).
Your answer would be 5(c-3).
