Rael's school organized a trip to Ireland. At first, the ratio of the number of girls to the number of boys who planned to participate in the trip was 7 : 5. On the day of registration, 12 boys decided to withdraw and 12 more girls decided to join in. In the end, the number of boys who participated became 35% of the total children for the trip. How many less boys than girls would visit Ireland in the end?

	Girls	Boys	Total
Before	7x5 = 35 u	5x5 = 25 u	12x5 = 60 u
Change	+ 4 u	- 4 u
After	13x3 = 39 u	7x3 = 21 u	20x3 = 60 u

35% = ³⁵₁₀₀ = ⁷₂₀

Since 12 boys withdrew and another 12 girls 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 boys who decided to withdraw
= 25 u - 21 u
= 4 u

4 u = 12

1 u = 12 ÷ 4 = 3

Number of less boys than girls in the end
= 39 u - 21 u
= 18 u
= 18 x 3
= 54

Answer(s): 54