It takes 12 cups of chicken broth to make a chicken soup recipe. how much is this in quarts?

3 quarts.

4 cups equal 1 quart according to the US standards.
Using that, we get an equation like:
4c = 1q
if you want 12 cups, you have to multiply the left side by 3 meaning you would also have to multiply the right side by 3.
3(4c) = 3(1q)
12c = 4q
you get 12 cups equals 4 quarts.