Question 620576
(r - 4s + 8) + (8r + 3s) + (s + 7)

r - 4s + 8 + 8r + 3s + s + 7

Combine like terms:

r + 8r = 9r

-4s + 3s = -1s

-1s + s = 0

8 + 7 = 15

The Answer:

9r + 15