#1

What is the value of |a²-b²| ? And how??

#2

Note that we are not told that (a) and (b) are integers.

(a^{-2}*b^{-3}=\frac{1}{a^2b^3}=?) So, basically we need to find the value of (a^2b^3).

(1) (a^{-3}*b^{-2}=36^{-1}) --> (a^3b^2=36). Not sufficient.
(2) (ab^{-1}=6^{-1}) --> (\frac{b}{a}=6). Not sufficient.

(1)+(2) Multiply (1) by (2): (a^3b^2*\frac{b}{a}=a^2b^3=36*6). Sufficient.