If the number of dogs in the neighborhood was originally half the number of cats in the neighborhood before twenty new dogs were born, and now there are twice as many dogs as cats, how many cats were in the neighborhood, to begin with, if there are 20 cats now?
Now there are twice as many dogs as cats, and if the number of cats is 20, there are 2*20=<<2*20=40>>40 dogs.
Before twenty new ones were born, the number of dogs in the neighborhood originally was 40-20=<<40-20=20>>20
If the number of dogs in the neighborhood was originally half the number of cats in the neighborhood, there were 20*2=<<20*2=40>>40 cats in the neighborhood.
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