13. Simplify the expression: \(\frac{7}{4}j \cdot 4k\)

To simplify the expression \(\frac{7}{4}j \cdot 4k\), we multiply the numerical coefficients and the variables separately.

Multiply the coefficients: \(\frac{7}{4} \cdot 4 = \frac{7 \cdot 4}{4} = 7\).

Multiply the variables: \(j \cdot k = jk\).

Combine the results: \(7jk\).

Ответ: \(7jk\)