15у-8у= 714
7у= 714
у= 714:7
у= 102
4х+5х+х= 1200
10х= 1200
х= 1200:10
х= 120
9у+у= 500
10у= 500
у= 500:10
у= 50
3х+7х+18= 178
10х+18= 178
10х= 178-18
10х= 160
х= 160:10
х= 16
7к+6к-13= 130
13к-13= 130
13к= 130+13
13к= 143
к= 143:13
к= 11
6у-2у+25= 65
4у+25= 65
4у= 65-25
4у= 40
у= 40:4
у= 10