Ответы и объяснения

2013-09-18T20:13:31+04:00
2х-13=15                                                                                                           
2х=15-13
2х=2
х=2:2
х=1
2013-09-18T20:14:50+04:00
2x-13=15
2x=15+13
2x=28
x=14

130-4x=70
4x=130+70
4x=200
x=50

9y-89=55
9y=55+89
9y=144
y=16