Question

Peter, Paul and Mary have $24 between them. Together Peter and Mary have double the amount of money that Paul has, while Paul and Mary together have the same amount of money as Peter. How much money does Peter have?

Answer 1

21

Answer 2

Let x,y,z be the amounts of the three, in the order named. Then

x+y+z = 24
x+z = 2y
y+z = x

Now solve for x.

Hint: it is not 21

Answer 3

x+y+z=24
-x+y+z=0

2y+2z=24
y+z=12
x=12