Resposta:

4-

a) 28, 35, 42, 49, 56, 63, 70, 77, 84, 91...

b) 30, 40, 50, 60, 70, 80, 90, 100, 110, 120...

c) 100, 125, 150, 175, 200, 225, 250, 275, 300, 325...