Simply just Add the different amounts of different crayons as your denominator, and find the number of red, as your numerator. This gets you 2/12. 2/12 = 1/6
If we have to find the chance of two thing happening (Getting two reds back to back) we have to multiply our chances. Think of how its harder to get the same thing twice in a row.
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.