Answer:

Explanation:
There are no numbers, only variables. So solving for "z" would mean we get an expression for z.
The equation given is:

We will cross multiply and use distributive property (shown below) to do our algebra and come up with an expression for z, in terms of a and b.
Distributive property: a(b - c) = ab - ac
So, lets solve:

This is the expression for z.