just need help with a quick proportionality question I may have lost my bearings on.
I am trying to write a single expression for $z$ in terms of $x$ and $y$ that corrsponds to this statement.
A unit increase in $x$ gives an increase $k$ in $z$ and a unit increase in $y$ gives an increase $l$ in $z$ where $k$ and $l$ are independent of $x$ and $y$.
I think the answer is $x+1=z(k+1)$ and $y+1=l(k+1)$ but I don't understand the statemnt '$k$ in $z$' and '$l$ in $z$' so am not sure if I'm correct.