First, graph each point on the coordinate plane. Now think of a vertical line moving from left to right. The line is always vertical. It starts at the left of the graph and moves to the right. If at any time, the line intersects more than one point, then the relation is not a function. If all the x-coordinates are different, the vertical line cannot touch more than one point at a time.
Think About It: If You work 1 times as long, you are working the same amount of time. If you are working more than 1 times as much, you would be working more hours.
