Question

Zack bought 7 shoes and 2 socks for $39. cody bought 5 shoes and two socks for $29.

Answer 1

Twenty pounds and 69 p

Answer 2

{unknown number}
shoe→$X 
sock→$Y

7X+2Y=39------------1
5X+2Y=29------------2

minus the first and the second,then 2Y would disappear
7X-5X=2X , 39-29=10
then you will have 2X=10 ,so X=5
take X=5 in each of the formula , then get Y=2