So this is going to be an exponential equation, which the format is 
, in which a is the initial value and b is the growth/decay rate.
In this case, a is going to be 340,000 and b is going to be 107%, or 1.07, since the population is going to be increasing by 7% and the equation is now
.
Now replace x with 12 and solve.
Solve
, and then if you don't round that answer and multiply it with 340000 you get 
.
In this case, a is going to be 340,000 and b is going to be 107%, or 1.07, since the population is going to be increasing by 7% and the equation is now
Now replace x with 12 and solve.
Solve