18. Simplify the expression: \(\frac{2}{5}u \cdot 7 \cdot 3v\)

To simplify the expression \(\frac{2}{5}u \cdot 7 \cdot 3v\), we multiply the numerical coefficients and the variables separately.

Multiply the coefficients: \(\frac{2}{5} \cdot 7 \cdot 3 = \frac{2}{5} \cdot 21 = \frac{42}{5}\).

Multiply the variables: \(u \cdot v = uv\).

Combine the results: \(\frac{42}{5}uv\).

Ответ: \(\frac{42}{5}uv\)