Answer:
12) v=0
13) w=9
14) y=5
15) z=-8
16) n=2, m=-2
17) x=3
18) 1, because
. Therefore

Explanation:
12) Exponent Zero rule. Anything raise to 0 power equals 1.
13) Exponent Negative rule:

14) Exponent Quotient rule:

In this case,

15) Exponent Product rule:

In this case,

16) Same rule as #15,

17)We can work backwards here, we know
and
, so we need
.
To achieve this, use Exponent Quotient rule, what x-4=1? x=5.
Similar base:
. Put
back for

18) 1*1*1*1=1. Anything raise to 0 power equals 1 (Exponent Zero rule). To prove this, any number(except 0) divided by itself equals 1.
Ex: 1/1=1, 4/4=1,
.
We can prove this with the Exponent Quotient rule.
. No matter how I write it, it's equal to 1.
The one exception is
, which is undefined, since dividing by zero is illegal.
Hope this helps. ;)