Since ln(x) is the inverse of e^x and we want to find out when P(x)=1000, we will substitute P(x) by 1000 and then solve for x days.
1600e^0.3x = 1000
Divide 600 for both sides you will get:
5/3 = e^0.3x
Multiply ( ln ) for both sides and then divide by 0.3.
(ln 5/3)/(0.3) = x
x = 1.7
So there will be 1000 flies in approximately 1.7 days
