23умн(x-12)=253
15умн(2x+11)=285
7умн(123-4x)=749

Пошаговое объяснение:

23*(x-12)=253

x - 12 = 253 : 23

x - 12 = 11

x = 11 + 12

x = 23

15*(2x+11)=285

2x + 11 = 285 : 15

2x + 11 = 19

2x = 19 - 11

2x = 8

x = 4

7*(123-4x)=749

123 - 4x = 107

4x = 123 - 107

4x = 16

x = 4

23(х - 12) = 253

23х - 276 = 253

23х = 253 + 276

23х = 529

х = 529/23

х = 23

15(2х + 11) = 285

30х + 165 = 285

30х = 285 - 165

30х = 120

х = 120/30

х = 4

7(123 - 4х) = 749

861 - 28х = 749

-28х = 749 - 861

-28х = -112

х = -112/-28

х = 4