Answer
a.) $ y = -5000x + 45000 $
b.) After 7 years the car's value will be $10000
c.) See attached image
Work Step by Step
$a.) \ m=\dfrac{ y_{2} - y_{1} }{ x_{2} - x_{1} } \longrightarrow -5000 = \dfrac{y - 45000}{x - 0} \longrightarrow -5000 = \dfrac{y - 45000}{x} \longrightarrow -5000x = y - 45000 \longrightarrow y = -5000x + 45000 $
$b.) \ 10000 = -5000x + 45000 \longrightarrow 10000 - 45000 = -5000x \longrightarrow -35000 = -5000x \longrightarrow x = \dfrac{-35000}{-5000} \longrightarrow x = \dfrac{35}{5} = 7$
