Answer:
When s = 20, r = 9
Step-by-step explanation:
Given,
s is directly proportional to (r + 1)
s = k(r + 1)
(k is the constant of proportionality)
When s = 8,
8 = k(3 + 1)
8 = k(4)
8 = 4k
8/4 = k
2 = k
When s = 20,
20 = 2(r + 1)
20 = 2r + 2
20 - 2 = 2r
18 = 2r
18/2 = r
9 = r