There were 45 more boys than girls, 4/5 of the boys and 2/3 of the girls passed the test. 49 children failed the test. How many girls were there ?

X Girls.

(x+45) Boys.

2x/3 girls passed the test.

(4/5)(x+5) = (4x/5 + 4) boys passed test

49 Children failed the test.

(x - 2x/3) = x/3 = Girls that failed the test.

(X+45) - (4x/5+4) = x/5+41 Boys that failed the test.

X/3 + (x/5+41) = 49
x/3 + x/5 = 49-41 = 8
Multiply both sides by 15:
5x + 3x = 120
8x = 120
X = 15 Girls.