Solve for both systems y + 8z = 139 and y+10z=173

y + 8z = 139

y + 8z-8z = 139-8z

y= 139-8z

y+10z=173

139-8z+10z=173

139+2z=173

139+2z-139=173-139

2z=34

2z/2=34/2

z=17

y= 139-8z

y= 139-8(17)

y= 139-136=3