10% of the people are performers for a concert and the rest are spectators. 70% of the spectators are parents and there are 1080 more parent spectators than child spectators. How many parent spectators must leave so that 26% of the people are parent spectators?

	Performers	Spectators
	1x10	9x10
		Children	Parents
		3x9	7x9
Before	10 u	27 u	63 u
Change			- ?
After	37x1 = 37 u		13x1 =  13 u

10% = ¹⁰₁₀₀ = ¹₁₀ 

70% = ⁷⁰₁₀₀ = ⁷₁₀ 

26% = ²⁶₁₀₀ = ¹³₅₀

The total number of spectators at first is repeated.  Make the total number of spectators the same.  LCM of 9 and 10 is 90.

Number of more parent spectators than child spectators at first
= 63 u - 27 u
= 36 u

36 u = 1080

1 u = 1080 ÷ 36 = 30

If some parent spectators leave, the total number of child spectators and performers remains unchanged.  

Number of parent spectators who must leave so that 26% of the people are parent spectators
= 63 u - 13 u
= 50 u
= 50 x 30
= 1500

Answer(s): 1500