Answer:
If z<7, then z-7 is negative, and |z-7| is positive. So, with the understanding that z-7 is positive, the first part of this expression becomes:
7-z for z<7
Similarly: if z<7, then z-9 is negative and |z-9| is positive. Thus, -|z-9| is equivalent to (9-z).
|z−7|−|z−9|, if z<7 becomes (7-z) - (9-z) for z<7. Simplifying this, we get:
7 - z - 9 + z = -2
