Answer
a) $y=17500x+875000$
b) 1,015,000 restaurants
Work Step by Step
a)
2008 had 945,000 restaurants
2004 had 875,000 restaurants
$2004-2004=0$
$2008-2004 = 4$
$(0,875000)$ and $(4,945000)$ are on the line
$m= (945000-875000)/(4-0)$
$m= 70000/4$
$m=17500$
$y=17500x+b$
$875000=17500*0+b$
$875000=0+b$
$y=17500x+875000$
b)
$2012-2004=8$
$y=17500x+875000$
$y=17500*8+875000$
$y=140000+875000$
$y=1015000$