X : 8=15:30

To solve the proportion \( \frac{X}{8} = \frac{15}{30} \), we can cross-multiply:

\[ X \times 30 = 8 \times 15 \]

Calculating the right side:

\[ 8 \times 15 = 120 \]

Now, we have:

\[ 30X = 120 \]

Next, we divide both sides by 30 to solve for \( X \):

\[ X = \frac{120}{30} = 4 \]

Therefore, \( X = 4 \).