B is 12
c is 6 because you don't count the zero
If the ratio of girls to boys in Mr. Hansen's class is 4:5, and the ratio of girls to boys in Ms. Luna's class is 8:10, then the equation that correctly compares the ratio of both Mr. Hansen's class and Ms. Luna's class are 4/5 = 8/10.
That's 33/100 and can't be simplified. If you had said that the 3s keep going and never end, then it would have been 1/3. But as written, it's just 33/100.