Estimate the instantaneous rate of change for x=2 for
y=x
y=x^2
y=7
If you mean the rate of change with respect to a change in x, that is the called the derivative.
For y = x, the derivative is 1
For y = x^2, the derivative is 2x (which is 4 when x = 2)
For y = 7, the derivative is 0. Y does not change and is independent of x.
If you mean the rate of the change in y with time, you would have to know the rate x changes in time.