Решим уравнения:
x = 720 / 6
x = 120
x = 400 * 380
x = 152000
x = 850 / 50
x = 17
x = 3600 / 900
x = 4
x = 1020 - 964
x = 56
x = 629 + 2871
x = 3500
Ответ: 1) 120, 2) 152000, 3) 17, 4) 4, 5) 56, 6) 3500.