1) (50-х)=(50-3х)×2
раскроем скобки
50-x = 100-6x
5x-50 = 0
5x = 50
x = 10
2) (2х+100)×8=12000
16x+800 = 12000
16x-11200 = 0
16x = 11200
x = 700
3) (300+х)×9=70×300
2700+9x = 21000
9x-18300 = 0
9x = 18300
x = 18300/9
х=2033,33333333
1) (50-х)=(50-3х)×2
раскроем скобки
50-x = 100-6x
5x-50 = 0
5x = 50
x = 10
2) (2х+100)×8=12000
раскроем скобки
16x+800 = 12000
16x-11200 = 0
16x = 11200
x = 700
3) (300+х)×9=70×300
раскроем скобки
2700+9x = 21000
9x-18300 = 0
9x = 18300
x = 18300/9
х=2033,33333333