Question 1000321
Hi there,
I assume that you want to know when 
the profit will $78 million.
P = t^2 - 2t + 15
t^2 - 2t + 15 = 78
t^2 - 2t - 63 = 0
(t + 7)(t - 9) = 0
t + 7 = 0
t = -7 (No answer as negative)
t - 9 = 0
t = 9
...............
So in 9 years or 2019
the profits will be $78 million
Proof:
P(t) = t^2 - 2t + 15
P(9) = 9^2 - 2(9) + 15
P(9) = 81 - 18 + 15
P(9) = 78.
Hope this helps :-)