Resposta:

30% de 330

330 ------------ 100%

 x   ------------ 30%

100* x = 330 * 30

100x = 9900

x = 9900 / 100       x = 99

15% de 315

315 ------------ 100%

x -------------- 15%

100*x = 315*15

100x = 4725

x = 4725/100

x = 47,25

90% de 225

225 -------- 100%

 x ---------- 90%

100*x = 225*90

100x = 20250

x = 20250/100

x = 202,50