The problem is:

If h(t) represents the height of an object above ground level at time t and h(t) is given by: h(t)= -16t^2 + 12t + 1. FInd the height of the object at the time when the speed is zero.

Also I dont understand the whole prime thing. For example, how would the following question be solved:

Suppose G(x)= 4x^2 + x + 4. Find a number B such that G'(b)=7.