This is very simple. You have 3 hens. They lay 3 eggs over 3 days. Well, make this easier on yourself. 1 egg=1 day.
So, the answer would definitely be 12 days from 3 hens=12 eggs.
Unless of course, the question was implying the 3 hens lay 3 eggs EACH, over 3 days. Meaning by the 3 day period, you'd have 9 eggs, meaning one hen lays 3 eggs in 3 days.
So, multiply 9*4, since 3*4=12 9*4=36, so by the 12 day period you'd have 36 eggs, but this is only if the question is implying EACH
The total 'parts' of the ratio is 10 (3+7). Complementary angles add to 90 degrees. Divide 90 by 10 and you get 9. Each 'part' is 9. 3:7 * 9 = 27:63 One angle is 27 degrees and the other is 63 degrees.