Question 1145367
Problem description is written badly.  


Maybe this is something like what it should be:
A computer system is 15000 dollars in value when new, and depreciates to 2600 dollars in eight years.  Assuming the value depreciation is linear with time, {{{P=MT+b}}} for P being value, T being time passage in years, find the equation in this form.


M, obviously the slope;
{{{M=(2600-15000)/8=-1550}}}


A known point  (T, P)  is  (0, 15000).

That shows the vertical axis intercept.
{{{highlight(P=-1550T+15000)}}}