Find the fourth proportion to 10, 12, and 15.

The correct option is 18.

Step-by-step explanation:

Let the fourth proportion to 10, 12, and 15 be x.

By definition, four numbers a, b, c, and d are in proportion if:

$\frac{a}{b}=\frac{c}{d}$

Here, a = 10, b = 12, c = 15, and d = x. Therefore, we can set up the proportion as:

$\frac{10}{12}=\frac{15}{x}$

Cross-multiplying to solve for x gives:

$10\×x=12\×15$

$10x=180$

Divide both sides by 10:

$x=\frac{180}{10}$

$x=18$

Thus, the fourth proportion to 10, 12, and 15 is 18.