Oliver had three boxes, containing a total of 1000 styrofoam cups. The number of styrofoam cups in Box W to the total number of styrofoam cups was 3 : 10. He sold 385 styrofoam cups from Box X and sold ¹₅ of the styrofoam cups in Box Y. The number of styrofoam cups left in Box X to the number of styrofoam cups left in Box Y was 4 : 1. How many styrofoam cups were there in Box X at first?

	Box W	Box X	Box Y	Total
Before	3 u	7 u (700)		10 u (1000)
		16 p + 385	5 p
Change		- 385	- 1 p
			4 p
After		4x4 = 16 p	1x4 = 4 p

10 u = 1000
1 u = 1000 ÷ 10 = 100

Number of styrofoam cups in Box X and Box Y at first
= 7 u
= 7 x 100
= 700

The number of cups left in Y is the repeated identity.
LCM of 1 and 4 = 4

16 p + 385 + 5 p = 700
16 p + 5 p = 700 - 385
21 p = 315

1 p = 315 ÷ 21 = 15

Number of cups in Box X at first
= 16 p + 385
= 16 x 15 + 385
= 240 + 385
= 625

Answer(s):625