540 : х + 15 = 150 : 2
540 : х + 15 = 75
(540 : х) = 75 - 15
540 : х = 60
х = 540 : 60
х = 9
х * 50 + 100 * 9 = 250 * 4
50х + 900 = 1000
(50х) = 1000 - 900
50х = 100
х = 100 : 50
х = 2
120 + х * 15 = 375
120 + 15х = 375
(15х) = 375 - 120
15х = 255
х = 255 : 15
х = 17
600 - 120 + х * 12 = 600
480 + 12х = 600
(12х) = 600 - 480
12х = 120
х = 120 : 12
х= 10
1260 + 12 * х = 3000
1260 + 12х = 3000
(12х) = 3000 - 1260
12х = 1740
х = 1740 : 12
х = 145