125 students choose to attend one of three after school activities: football, tennis or running. There are 56 boys.
50 students choose football, of which 22 are girls.
40 students choose tennis.
28 girls choose running.
A student is selected at random.
What is the probability this student chose running?
Give your answer in its simplest form.

The answer that i got was 8/3

So the first thing we do is to multiply the top equation by 3. the reason i want to do this is i notice there will be a 6y on both equations and can possibly add/subtract them. so we get 6y = -3x + 27. adding that and the second equation we get 6x = 27-15 which is 12. divide by 6 and we get 2. ∴ x = 2. substituting 2 into the first equation we get 2y = -2 + 9 which is 7. divide by 2 and we get 7/2. ∴ y = 7/2, x = 2.