Levi's school organized a trip to Scotland. At first, the ratio of the number of boys to the number of girls who planned to participate in the trip was 7 : 5. On the day of registration, 128 girls decided to withdraw and 128 more boys decided to join in. In the end, the number of girls who participated became 15% of the total children for the trip. How many more boys than girls would visit Scotland in the end?

	Boys	Girls	Total
Before	7x5 = 35 u	5x5 = 25 u	12x5 = 60 u
Change	+ 16 u	- 16 u
After	17x3 = 51 u	3x3 = 9 u	20x3 = 60 u

15% = ¹⁵₁₀₀ = ³₂₀

Since 128 girls withdrew and another 128 boys joined, the total number of children  at first and in the end remains unchanged. Make the total number of children the same. LCM of 12 and 20 is 60.

Number of girls who decided to withdraw
= 25 u - 9 u
= 16 u

16 u = 128

1 u = 128 ÷ 16 = 8

Number of more boys than girls in the end
= 51 u - 9 u
= 42 u
= 42 x 8
= 336

Answer(s): 336