We are given the function:

And the table contains two values of y (-16 and -64) for whose we need to find the corresponding values of x.
For y = -64:

Applying properties of the exponents:

Get rid of the bases, we equate the exponents:
x = -3
For y = -16:

Applying properties of the exponents:

Equating the exponents:
x = -2
The values of the table are:
-2 , 16
-3 , 64