They give you f(380)=16, a.k.a. they've given you a point (x,y). They also give you f'(380)=8, so you know the slope of the tangent at that point.
Since we're estimating, you have three points and the slope, which give you enough information to estimate the fourth point.
(y1-y2)/(x1-x2) = m
Plug in and solve for the y value which is f(383).
At least, I think that's what they want you to do.