Question 118706
if 1980 -> t=0 then, 1986 -> t=6 (six years later).
The two points are (t,price) -> (0,100000) and (6, 112000)

we want an equation in the form y=mx+b,
the y-intercept(b) is the y(P in this problem) value when x(t in this problem) is 0: so b=100000
m is the slope: m={{y2-y1}/{x2-x1}}={{t2 - t1}/{P2 - P1}}
so m = {{112000-100000}/{6-0}} = 2000

so y = 2000x + 100000
or P = 2000x + 100000 and the answer is C.