Y: X = 5: 6 because the first prize of school A and school B is the same.

The number of people who won the second prize in A school is 4.5 times that of B school, and the total number of people who won the second prize is 5.5 times that of B school.

The total number of people who won the second prize in the two schools accounted for 20% of the total number of winners in the two schools.

The total * * * second prize is 1/5(x+y)

So the number of people who won the second prize in school B is 1/5(x+y)/5.5, and the number of people who won the second prize in school A is 1/5(x+y)/5.5*4.5.

The number of people who won the third prize in a school accounts for 50% of the school's winners.

So a school won the first prize of1/2x-[1/5 (x+y)/5.5 * 4.5].

School B won the first prize1/2x-[1/5 (x+y)/5.5 * 4.5] = 0.5x-9/55 (x+y), y: x = 5: 6; y=5a，x=6a

Percentage of B: 6/5a/(5a)=6/25=24%.