The equation for working out the slope of a linear line is: 
, where x and y are the coordinate pairs.
So just pick two of the purple dots on the graph and fill in the equation.
I'll pick the dot that's (-4, 1) and (4, -7).
Now I just do 
, which is just 
when simplified.
Multiply 209 by 12 to find one year which is 2508
Multiply 2508 by 4 to find 4 years which is 10032
Subtract 8500 from 10032 which is 1532
So he paid 1532 more than the cars original price
I hope thats understandable!
The side is (2x+3)? then the area is:
(2x+3)(2x+3) = 4 x^2 + 12 x + 9 if x = 6 then
Area = 4(36)+12(6)+9
= 144 + 72 + 9
= 225, too big :(
Exercise regularly.
Do not smoke or use tobacco products.
Get plenty of rest.
Eat a balanced diet.
