Question:
Express $\frac{-42}{98}$ as a rational number with denominator 7 .
Solution:
If $\frac{a}{b}$ is a rational number and $m$ is a common divisor of $a$ and $b$, then $\frac{a}{b}=\frac{a \div m}{b \div m}$.
$\therefore \frac{-42}{98}=\frac{-42 \div 14}{98 \div 14}=\frac{-3}{7}$