A more general way is to use the formula y2 - y1 x2 - x1 where y2 is a result of whatever expression you started with so here 100 dollars for 8 hours which means you could say 100 is one output. Slope y 2 y 1 x 2 x 1 How it works. Determine the slope of the line passing through the points.
See the graph below.
It is based on the slope. Use the equation of rise over run which is Y2-Y1 divided by X2-X1. Just type numbers into the boxes below and the calculator will automatically find the slope of two points. When the line is graphed m is the slope of the line and b is where the line crosses the y-axis or the y-intercept.