6v=18

6v/6=18/6

v=3

4v+x = 16

4(3)+x = 16

12+x = 16

12+x-12 = 16-12

x=4

2v+4x+2z = 24

2(3)+4(4)+2z = 24

6+16+2z = 24

22+2z = 24

22+2z-22 = 24-22

2z=2

2z/2=2/2

z=1