math
posted by hates math .
Colin is working to earn some money for a CD player.On Saturday he earned half as much as he did on Sunday,but twice as much as he did on Friday.During those three days he earned $70.How much did he earn each day?

let Sat's earnings be x
Sunday = 2x
Friday = x/2
x + 2x + x/2 = 70
7x/2 = 70
x = 20
Friday: 10
Saturday: 20
Sunday: 40