Question

х+3-123=123,,,,,,,,,,,,

Answer 1

х+3-123=123
х+3=123+123
х+3=246
х=246-3
х=243
Проверка
243+3-123=123
246-123=123
123=123

Answer 2

x+3-123=123
x-120=123
x=120+123
x=243