x:13=57:39

To solve the equation \( x:13 = 57:39 \), we can set up a proportion.

This can be written as:

\[ \frac{x}{13} = \frac{57}{39} \]

Cross-multiplying gives us:

\[ x \cdot 39 = 57 \cdot 13 \]

Calculating \( 57 \cdot 13 \):

\[ 57 \cdot 13 = 741 \]

So, we have:

\[ 39x = 741 \]

Now, divide both sides by 39 to solve for \( x \):

\[ x = \frac{741}{39} \]

Calculating \( \frac{741}{39} \):

\[ x = 19 \]

Therefore, the solution is:

\[ x = 19 \]