To evaluate the multiplication of a positive fraction and a negative integer variable term, such as $\frac{13}{7}(-14b)$, first determine the sign of the product. Since the terms have different signs, the product is negative. Write the integer term as a fraction, $-\frac{14b}{1}$, and multiply the numerators and denominators to yield $-\frac{13 \cdot 14b}{7 \cdot 1}$. Rewrite the numerator to expose the common factor of $7$, giving $-\frac{13 \cdot 2 \cdot 7b}{7}$. Finally, divide out the common factor of $7$ to simplify the expression, resulting in $-26b$.