Решение:
- 1) 390/650 = (390 ÷ 130) / (650 ÷ 130) = 3/5
- 2) 4550/5550 = (4550 ÷ 50) / (5550 ÷ 50) = 91/111
- 3) 570/13310 = (570 ÷ 10) / (13310 ÷ 10) = 57/1331 = (57 ÷ 19) / (1331 ÷ 19) = 3/7
- 4) 4200/4550 = (4200 ÷ 50) / (4550 ÷ 50) = 84/91 = (84 ÷ 7) / (91 ÷ 7) = 12/13
Ответ: 1) 3/5; 2) 91/111; 3) 3/7; 4) 12/13