To convert from feet to miles divide by 5280. To convert inches to feet divide by 12.
For 3 think of a x and y graph. The X represents an independent value or a value that is not affected like time, and Y represents a dependent value which is affected by another value. Y would be the price because it is affected by time. Now think of slope (rise/run). The "rise" is how high or low you are going and the "run" is how far you travel from left to right. The "rise" will be the fall in price which is $200, and the "run" will be 4 years. Rise/Run or 200/4 , which happens to be 50. But remember it is falling, so it is negative. -50 will be the slope. Do you know the point slope formula? Well this is when you use it. y=mx+b. The y and x will be the x and y coordinates, the m is the slope, and the b is the y-intercept. Plug "m" with -50. Then a coordinate. like (1998,800). Then solve for b, which is 41998. The equation to use for the rest of this problem is y=-50X+41998.