Answer:
1/2
Step-by-step explanation:
Probably of selecting a boy:
20/30 = 2/3
and brought 10 up to 20:
45/60 = 3/4
so Probably of selecting a boy and brought 10 up to 20:
2/3 x 3/4 = 2/4 = 1/2
2:1
I took the test
