whichever number you pick (5-50) is represented by 'X'
'X' will be the amount of money you saved a week
The weeks are going to be represented by 'Y'
so the formula would be-
'X' x 'Y'= The amount of money saved over 4 years of high school
So you have to get the number of weeks in four years and multiply it by the number that you selected and that should give you the answer.
Hope this Helps :)