For most people the ratio of the length of their head to their total height is 1: 7 use proportions to test your measurements and see if they match this ratio

The correct answer for this question is this one: 5 / 7

There exists the same question from other source that has the continuation of the problem. Use proportions to test your measurements and see if they match this ratio. Height is 5ft

So this how to solve this:

Set the equation as:
7x = 5
x = 5 / 7

X= 2 he can buy 2 packs of cards for $12 and an action figure for $3 so he would spend $15 in total plus the free poster