Question:
Solve:
$\frac{2-9 z}{17-4 z}=\frac{4}{5}$
Solution:
$\frac{2-9 z}{17-4 z}=\frac{4}{5}$
$\Rightarrow 5(2-9 z)=4(17-4 z) \quad$ (by cross multiplication)
$\Rightarrow 10-45 z=68-16 z$
$\Rightarrow 10-68=45 z-16 z$
$\Rightarrow-58=29 z$
$\Rightarrow 29 z=-58 \quad$ (by transposition)
$\Rightarrow z=\frac{-58}{29}=-2$
$\therefore z=-2$