Find the size of angle XZY give your answer

Which expression is equivalent to (3^2)^-2 a.-81 b.-12 c.1/81 d.1/12

Ineed with number 6 , explain how to get 1978

Aclassmate thinks that solving a system by graphing gives an exact answer when the lines appear to cross at a grid point, but only an approximate answer when they don't. explain why this isn't true.