@jemidiah: You mixed up your variables.

Assuming a linear equation (y = mx + b), we can solve for the first two equations to find m = -0.39700919 and b = 11.793277. This result fits well with the third equation.

f(x) = 11.793 - 0.397x

f(27.1864667) = 0.9999727201
f(24.6676333) = 1.999949699
f(2.2479) = 10.9005837