Question

how would I make a table of x and y values for x = ( - 1/3 )y?

Answer 1

Pick a y, write that in the y column, then multiply it by (-1/3) and write the result in the x column.
It would probably be smart to pick y values that can easily by multiplied by (-1/3). For example, you probably know off the top of your head what a third of 3 is.