Justin, Pierre and Christopher collected cards in the ratio of 10 : 7 : 8. After Christopher gave ³₄ to Justin and Pierre, Christopher had 336 less cards than Justin. The number of cards that Pierre had increased by 80%. How many cards did Justin and Christopher have in the end?

	Justin	Pierre	Christopher
Before	10 u	7 u	8 u
Change	+ 0.4 u	+ 5.6 u	- 6 u
After	10.4 u	12.6 u	2 u

Number of cards that Christopher gave to Justin and Pierre
= ³₄ x 8 u
= 6 u

Number of cards that Pierre received from Christopher
= ⁸⁰₁₀₀ x 7 u
= 5.6 u

Number of cards that Justin received from Christopher
= 6 u - 5.6 u
= 0.4 u

Number of less cards that Christopher had less than Justin
= 10.4 u - 2 u 
= 8.4 u

8.4 u = 336

1 u = 336 ÷ 8.4 = 40

Number of cards that Justin and Christopher had
= 10.4 u + 2 u
= 12.4 u
= 12.4 x 40
= 496

Answer(s): 496