algebra
posted by Penny .
A boat is worth $7,000 when it is 5 years old and $2,000 when it is 10 years old. What is the slope intercept equation?

You have two points: (5,7000) and (10,2000)
the twopoint equation for the line is thus
(y7000)/(x5) = (20007000)/(105)
or, after rearranging things a bit:
y = 1000x + 12000
That is, the value started at $12,000, and depreciates $1000/year