Ответ:

(450 - 300) • x = 450

150 • x = 450

x = 450 : 150

x = 3

x - (315 - 245) = 526

x - 70 = 526

x = 526 + 70

x = 596

(859 - 259) : x = 200

600 : x = 200

x = 600 : 200

x = 3