💥 Q 72: Prep 3 Algebra Question Bank T1

If \( \frac{21 \, X - y}{7 \, X - z} = \frac{y}{z} \), prove that: \( y \propto z \)

Using cross multiplication:

\( (21X - y) \cdot z = (7X - z) \cdot y \)
\( 21Xz - yz = 7Xy - zy \)
\( 21Xz = 7Xy \)
\( 3z = y \)
Therefore, \( y \propto z \)