In a store, some rubber balls and toy cars were on sale. ¹₅ of the items were rubber balls. ¹₃ of the rubber balls and 561 toy cars were sold. There were ¹₁₂ of the items left in the store. How many rubber balls and toy cars were there in the store at first?

	Rubber balls	Toy cars	Total
Comparing rubber balls  and toy cars at first	1x12 = 12 u	4x12 = 48 u	5x12 = 60 u
Before	3x4 =  12 u		12x5 = 60 u
Change	- 1x4 = - 4 u	- 561	- 11x5 = - 55 u
After	2x4 = 8 u	-3 u	1x5 = 5 u

 
The total number of toys at first is repeated.  Make the total number of toys at first the same. LCM of 5 and 12 is 60.

The number of rubber balls at first is repeated.  Make the number of rubber balls the same. LCM of 12 and 3 is 12. 

Number of toy cars left
= 5 u - 8 u
= -3 u

Number of toy cars sold
= 48 u - -3 u
= 51 u

51 u = 561

1 u = 561 ÷ 51 = 11

Number of rubber balls and toy cars at first
= 60 u
= 60 x 11
= 660

Answer(s): 660