Jawaban:

2(s + 3) + 7(s – 3) = 5(s – 1)

2s + 6 + 7s – 21 = 5s – 5

2s + 7s + 6 – 21 = 5s – 5

9s – 15 = 5s – 5

9s – 5s = 15 – 5

4s = 10

s = 10/4

s = 5/2

2s = 2(5/2)

2s = 5