Ответы и объяснения

2014-04-07T19:06:07+00:00
5(х+3)+7 = 3(х+12)
5х+15+7 = 3х + 36
2х = 36-15-7
2х = 14
х = 7

5(7+3)+7 = 3(7+12)
57=57
2014-04-07T19:20:06+00:00