Answer
a) $y=-6000x+267000$
b) 159,000 dollars
Work Step by Step
a)
7 years after purchase, valued at 225000
12 years after purchase, valued at 195000
$m=(225000-195000)/(7-12)$
$m=30000/-5$
$m=-6000$
$y=mx+b$
$y=-6000x+b$
$225000=-6000*7+b$
$225000=-42000+b$
$267000 = b$
$y=-6000x+267000$
b)
$2013-1995=18$
$y=-6000x+267000$
$y=-6000*18+267000$
$y=-108000+267000$
$y=159000$