What is the rate of change for f(x) =-0.9x+665

The rate of change is -0.9.

Since the function f defined by f(x) = -0.9x + 665 is in slope-intercept form
f(x) = mx + b, we identify the coefficient on x to be the slope. And the slope is the rate of change.

For every one unit increase in x, y decreases by 0.9 units.

The median is going to be 35