Question

what is x-5* 1+b if x is 10 and b is 20

Answer 1

plug them in.
x(10) - 5 equals what? 5 right?
1 plus b(20) equals? 21
then if im not mistaken you have "*" in your problem so you'd multiply those two answers and get you final answer.

Answer 2

if x is 10 then the equation would be 10-5*1+b
If b is 20 the equation would be 10-5*1+20