Answer:
$ 2000
Step-by-step explanation:
Find the equation. You find the gradient by using the gradient formula (rise/run)
that would be
1600 - 800 over 40 - 20
800/20
m (gradient) = 40
Hence 40x ...
v = 
given d = 
multiply both sides of the equation by v, hence
dv = m ( divide both sides by d )
v = 
Actually the line would be y=x/2 -3, this is in y=mx+b form. And normally they give you the ordered pairs.