1)

A = 20

B = 4

B = A * 2 = 40

A = B - 5 = 35

40

2)

A = 5

B = 5

B = 10

A = A - 5 = 0

10 + 0 = 10

3)

A = 4

B = 6

C = 8

C = 10

B = 4 + 10 = 14

A = B + C = 14 + 10 = 24

24