Question 252188
This question requires you to set up a system of equations. Let B = books, and C = candy. 
The first sentence becomes: 20 = B + C. 

50% more than means 100% last week + 50% this week or 150%, which is 3/2
12.5% less than means 100% last week - 12.5% this week or 87.5% which is 7/8.
The second sentence becomes: 20 = (7/8)B + (3/2)C

multiplying the second equation by 8, we get: 160 = 7B + 12C.


Now we have
20 = B + C
160 = 7B + 12C

step 1 - multiply the first equation by -7. This gives us

-140 = -7B -7C
160 = 7B + 12C

step 2 - add down to get

20 = 5C

step 3 - solve for C. C = 4. She spent $4 on candy LAST week. This week, it was $6.