y=mx+b is the formula. So -8=-3x+5would be the answer..
since (x,y) just substitute these numbers you have it into the formulas... Take y from (5,-8) and place it into y=mx+b. Next take the slope which is -3. And then since its a postive number we <em>add</em> are x from (x,y). -8=-3x+5. We also add x next to the slope (-3) becuase we are trying to solve for x. And we <em>always</em> put it next to the slope. Hope this helps!