Seniors & juniors algebra word problem

The original question comes from http://homeschoolmath.blogspot.com/

Question

The total number of girls in the combined junior and senior classes is equal to the number of boys in those two classes. If the senior class has 400 students and the junior class has 300 students, and if the ratio of boys to girls in the senior class is 5:3, what is the ratio of boys to girls in junior class?

Answer

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Primary 5 Problem Sum

Question

2/9 of the runners in a race are boys.3/7 of the remaining runners are men.1/4 of the rest are girls. There are 42 more women than girls. How many runners are there in the race?

Answer