Need Help finding Instantaenous Velocity

[Bryanaam]

Truck rolls down a Ramp at s(x)=3X^3 + 2x^2 + 4
I need to find Instantaneous velocity at x=4 seconds... The intervals are between 0<x<4. I can't think of the answer.. I know that I'm supposed to get the derivative of it, but then I'm unsure of what to do with that..

 

[HallsofIvy]

Surely, since you refer to the derivative, you know that the derivative is the derivative of the position function with respect to time. Since you are asked for the instantaneous velocity at x= 4 you evaluate the derivative function at x= 4.