In this task, you need to provide the correct option for a given problem from the provided options.

Q: Problem: in a group of 22 boys , 13 play basketball and 15 play football . 3 of the boys play neither . how many play both ? 
Options: a ) 18 , b ) 20 , c ) 21 , d ) 22 , e ) 25

A: a
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Q: Problem: bag a contains red , white and blue marbles such that the red to white marble ratio is 1 : 3 and the white to blue marble ratio is 2 : 3 . bag b contains red and white marbles in the ratio of 1 : 4 . together , the two bags contain 40 white marbles . how many red marbles could be in bag a ? 
Options: a ) 8 , b ) 3 , c ) 4 , d ) 6 , e ) 8

A: a
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Q: Problem: a certain fraction has the same ratio to 1 / 18 , as 2 / 5 does to 2 / 9 . what is this certain fraction ? 
Options: a ) 1 / 5 , b ) 1 / 7 , c ) 1 / 10 , d ) 1 / 12 , e ) 1 / 15

A:
c
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