t represents the number of years after 2005 so in 2007, t = 2 and N = 2546
In 2012, t = 7 as it is seven years after 2005 and N = 2702.
This of this as ordered pairs but instead of x and y you have t and N,
You need a slope so instead of (y2- y1)/(x2-x1) =m, you now have m = (N2-N1)/(t2-t1)
m = (2702-2546)/(7-2) or 31.2.
Normally, you'd use the slope point equation for a line y-y1 = m(x - x1) but we are using N for y and t for x.
Pick one or the pairs of values, say t=2 and N =2546
N-2546=31.2 (t-2) and solve for N= 31.2 t+2483.6..
Then substitute in 3000 for N to find the time it reaches 3000. Remember to add your answer to 2005 since t is the number of years past 2005.