Could someone help on my algebra question?

It's kind of hard to read but I think I've identified three lattice points on the graph,

(-6,-3), (0,-1), (9,2)

Calculating slopes, change in y over change in x

(-1 - -3) / (0 - -6) = 1/3

(2 - -1) / (9 - 0) = 1/3

Those agree so we conclude

Slope 1/3

It's a line; it doesn't really start anywhere.  Let's use the y intercept:

Starting Value: at x=0 we start at y=-1

We have a slope and a y intercept so our equation is

y = (1/3)x - 1

Check:

(1/3)(-6)-1 = -3, good

(1/3)0 - 1 = -1, good

(1/3)(9) - 1 = 2, good