Solve the equation for the unknown variable z3=-64

Z= -21.33 approximately because you divide both sides of the equation by 3, resulting in -64/3, which is about -21.33

When they ask for X, you are generally supposed to look at all the points in which the line intercepts the X axis. So that would be -2, 1, and 3.

PS. even if it asked for Y, instead of X, you would do the same thing.