15y-8y=714
7y=714
y=714:7
y=102
9z+z=500
10z=500
z=500:10
x=50
10k-k=702
9k=702
k=702:9
k=78
4l+l+l=1200
6l=1200
l=1200:6
l=200
6t+3t-t=6400
8t=6400
t=6400:8
t=800
15y-8y=714
7y=714
y=714:7
y=102
9z+z=500
10z=500
z=500:10
x=50
10k-k=702
9k=702
k=702:9
k=78
4l+l+l=1200
6l=1200
l=1200:6
l=200
6t+3t-t=6400
8t=6400
t=6400:8
t=800