#### Answer

There is 16.25 percent of grapefruit juice in the resulting mixture.

#### Work Step by Step

Let X represent the amount of grapefruit in the mixture.
Since the first mixture is 30 ounces and the second mixture is 50 ounces, the resulting mixture will be 30 + 50 = 80 ounces.
To find X, the amount of grapefruit in the mixture, we use the following guideline:
Amount of grapefruit in the first solution + amount of grapefruit in the second solution = Amount of grapefruit in the final solution.
10% $\times$ 30 + 20% $\times$ 50 = X
$.1 \times 30 + .2 \times 50 =X$
3 + 10 = X
X = 13
There are 13 ounces of grapefruit in the 80 ounce mixture.
Since we need to calculate the percentage of grapefruit juice, we proceed:
$\frac{13}{80}$ $\times$ 100% = 16.25%