In a boarding kennle, dogs number 12 more than 2 times the number of cats. If there are 75 animals, how many cats are boarded?
Let d stand for number of dogs and c stand for number of cats.
d = 2*c + 12 ...(1)
d + c = 75 ...(2)
Replace d in (2) using (1)
2*c + 12 + c = 75
3*c + 12 = 75
3*c = 75 - 12
3*c = 63
c = 63/3
c = 21
So there are 21 cats (and 2*21 + 12 = 54 dogs)
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