Answer
True.
If we multiply $z$ by a factor $k$, then $x$ will also be multiplied by the same factor $k$ and, consequently, y will also be multiplied by $k$.
Work Step by Step
$a,b,c$ are constants.
$y=ax$
$x=bz$. Replace this equation in the above equation.
$y=a(bz)=(ab)z=cz$
$y=cz$, where $c=ab$
