To set up a proportion for the statement "15 is x% of 60," we can write it as:
\[ \frac{15}{60} = \frac{x}{100} \]
Next, we'll use cross multiplication to solve for \(x\):
Cross multiplying gives us:
\[ 15 \cdot 100 = 60 \cdot x \]
Calculating the left side:
\[ 1500 = 60x \]
Now, divide both sides by 60 to solve for \(x\):
\[ x = \frac{1500}{60} \]
Calculating that gives:
\[ x = 25 \]
Therefore, 15 is 25% of 60.