Mark had three boxes, containing a total of 910 plastic plates. The number of plastic plates in Box F to the total number of plastic plates was 3 : 7. He sold 481 plastic plates from Box G and sold ¹₅ of the plastic plates in Box H. The number of plastic plates left in Box G to the number of plastic plates left in Box H was 2 : 1. How many plastic plates were there in Box G at first?

	Box F	Box G	Box H	Total
Before	3 u	4 u (520)		7 u (910)
		8 p + 481	5 p
Change		- 481	- 1 p
			4 p
After		2x4 = 8 p	1x4 = 4 p

7 u = 910
1 u = 910 ÷ 7 = 130

Number of plastic plates in Box G and Box H at first
= 4 u
= 4 x 130
= 520

The number of plates left in H is the repeated identity.
LCM of 1 and 4 = 4

8 p + 481 + 5 p = 520
8 p + 5 p = 520 - 481
13 p = 39

1 p = 39 ÷ 13 = 3

Number of plates in Box G at first
= 8 p + 481
= 8 x 3 + 481
= 24 + 481
= 505

Answer(s):505