If you plot the equations for both length and width on a graph, making them both equal to y of course, you find that they cross each other in two places. The places they cross are (81, 11) and (70, 0). It is impossible for the answer to have the width as 0 feet, so the answer is 81 feet.
1. To find the slope, we need to have the equation in slope-intercept form, which is . In this case, our equation is already in this form. is what your slope is. In this case, our
2. To find the y-intercept we look at value that is in . In this case, is . So, our ordered pair is .