Question

12
?
24
15
25

Explanation:

Step1: Assume the two trapezoids are similar.

For similar - shaped figures, the ratios of corresponding sides are equal.

Step2: Set up the proportion.

Let the unknown side be $x$. The ratio of the corresponding upper - bases is the same as the ratio of the corresponding non - parallel sides. So, $\frac{12}{15}=\frac{x}{25}$.

Step3: Cross - multiply to solve for $x$.

$15x = 12\times25$.
$15x=300$.
$x=\frac{300}{15}=20$.

Answer:

20