If 5a = 25 and 5b = 625 what is 5b-a?

Think about the individual parts of the expression.

5b - a

5b equals 625. Therefore, 5b - a = 625 - a

Now you have 625 - a.

If 5a = 25, then what does "a" equal? Divide 5 from both sides to find out.

5a/5 = 25/5

a = 5

Therefore, 625 - a = 625 - 5

625 - 5 = 620

620 is the answer.