Ivan, Ahmad and Corwin collected buttons in the ratio of 10 : 9 : 6. After Corwin gave ⁷₁₀ to Ivan and Ahmad, Corwin had 575 less buttons than Ivan. The number of buttons that Ahmad had increased by 10%. How many buttons did Ivan and Corwin have in the end?

	Ivan	Ahmad	Corwin
Before	10 u	9 u	6 u
Change	+ 3.3 u	+ 0.9 u	- 4.2 u
After	13.3 u	9.9 u	1.8 u

Number of buttons that Corwin gave to Ivan and Ahmad
= ⁷₁₀ x 6 u
= 4.2 u

Number of buttons that Ahmad received from Corwin
= ¹⁰₁₀₀ x 9 u
= 0.9 u

Number of buttons that Ivan received from Corwin
= 4.2 u - 0.9 u
= 3.3 u

Number of less buttons that Corwin had less than Ivan
= 13.3 u - 1.8 u 
= 11.5 u

11.5 u = 575

1 u = 575 ÷ 11.5 = 50

Number of buttons that Ivan and Corwin had
= 13.3 u + 1.8 u
= 15.1 u
= 15.1 x 50
= 755

Answer(s): 755