Question

how do i do 45/a - 2 for a  = 5
                  

Answer 1

just substitute 5 for a, and get 45/5 and then get 9, so the final answer is 7 because you subtract two.

Answer 2

$a = 5\\ \\\frac{ 45}{a} - 2 =\frac{45}{5}-2 =9-2=7$