Alice has twice as many stamps as Betty. Mary has 3 times as many stamps as Alice. If Mary has 20 more stamps than Betty, how many stamps do the three girls have?

Answer 1

A = 2*B

M = 3*A

M = B + 20

A = 2*(M - 20) = 2*((3*A) - 20) = 6A - 40

A = 40/5 = 8

M = 24

B = 4