Maia mixed a batch of punch for the class party. her recipe called for 4 2/5 cups
of orange juice, 3 1⁄2 cups lemonade, and 12 3/4 cups of ginger ale. how many 1-cup servings does the recipe make?

You just have to add all the amounts of the ingredients.
4 2/5 + 3 1/2 + 12 3/4

You can first add all the whole numbers
4 + 3 + 12 = 19

Then, you can add all the fractions
2/5 + 1/2 + 3/4

To add all the fractions, you have to use the LCD. The LCD is 20. So, divide 20 with the denominator of each fraction and multiply the result with the numerator. The denominator of all fractions would now be 20.

So,
(2x4 + 1x10 + 3x5) / 20
(8 + 10 + 15)/20
33/20

The answer is an improper fraction. We divide 33 by 20 and get the remainder.
33/20 = 1 13/20

We have a whole number of 1, we add this to the sum of the whole numbers we got earlier.
19 + 1 =20

Finally, we put together the whole number and the remainder (fraction)
20 13/20.

Therefore, the recipe can make 20 1-cup servings. The remaining 13/20 can't make a full-sized cup.