The line y=-1/7x or -x/7 has a negative shallow slope which means it slopes backwards (\). It passes through the origin (0,0) where the x and y axes cross. When x=7 y=-1 so we have two points (7,-1) and (0,0) such that if you draw a straight to pass through these two points extended in both directions you have the required graph. Just to make sure, check that the point (-7,1) also lies on the line.