7y+6z=151
7y-7y+6z=151-7y
6z=151-7y
6z/6=151-7y/6
z=25.67-1.167y
13y + 4z = 209
13y + 4(25.67-1.167y) = 209
13y + 4(25.67) (4)(-1.167y) = 209
13y + 102.68-4.67y = 209
8.33y +102.68= 209
8.33y +102.68-102.68= 209-102.68
8.33y=106.32
8.33y/8.33=106.32/8.33
y=12.76
z=25.67-1.167y
z=25.67-1.167(12.76)
z=25.67-14.90=10.77