This is the very last time I will bug you calc geniuses, but I'm (yet again) stuck. It's a linear approximation question dealing with atmospheric pressure. I have figured out the kPa for 1000 m and 2000 m, but need to figure out the kPa for 3000 m. Anyway, here's the problem:
At a temp of 15 deg. C, the pressure is 101.3 kPa at sea level, 87.1 kPa at 1000 m, 74.9 kP at 2000 m. use a linear approximation to estimate the atmospheric pressure at an altitude of 3000 m.

I figured K=1.51 *10^-4 for 1000 m, 1.51*10^-4 for 2000 m, and (I think) the kPa for 3000 is about 73 kPa, but I'm not sure how to prove it using linear approximation.

Anyway, thanks for the help!