Question 252128
Crystallina spent her entire $ 20 weekly allowance on books and candy last week. This week she did the same, but she spent 50 % more on candy and 12.5 % less on books.How much did she spend on candy this week?

Let x be the amount she spent the first week on books and y the amount on candy. 

Then:

x + y = 20 or
y = 20 - x

The second week then we have:

.875x + 1.5y = 20

Substituting 20-x for y in the second equation we have:

.875*x + 1.5*(20 - x) = 20 

Solve for x and then calculate y = 20 - x.