How do you do this, i can't figure it out

I'm going to assume you mean a line going through (2,0) with a slope of 1/4. Is that correct?

The general equation for any line is
y = mx+b
m is the slope 
m = 1/4 

so what you have so far is y = (1/4)x + b

Now what you do is use the point (2,0) to solve for b. What this is saying is that when x = 2, y =0. Substitute.
0 = (1/4)*2 + b
0 = 1/2 + b Subtract 1/2 from both sides.
b = -1/2

y = (1/4)x - 1/2 <<<< answer. Just so you know, I'm including the actual graph.

She will need 5/8 bags for each square yard.