Identify the slope, m. This can be done by calculating the slope between two known points of the line using the slope formula.
or
Find the y-intercept. This can be done by substituting the slope and the coordinates of a point (x, y) on the line in the slope-intercept formula and then solve for b.
You would use rise over run. So if you have a graph and you trying to figure out the slope you count up the (or down) and then to the side. the rise is first and then the run. you would then display it as a fraction with the rise being the numerator and the run being the denominator. If you have to count down on the graph for the run instead of up (this happens when the graph is decreasing) the rise would be negative(because your going down). if you have to go left on the graph for the run it would be negative (because left on a graph is decreasing)
When using slope intercept from, Y = mx + b. M is slope. if the slope is a whole number to find the rise over run you add a 1 to the denominator and then you have your rise over run.
ask your self frist how many months is in 6 years that would be 72 months .....so now you have 8.5% interest on the amount of $4280 for 72 months.....the interest gained in 72 months would be $3047.37......$4280+$3047= $8727. I think but not 100% sure
