I am having trouble answering this problem. Please offer any suggestion. There are several parts to be answered:

1) An object moves along the x axis according to the equation x(t) = (3.90t2 - 2.00t + 3.00) m.

a) Determine the instantaneous speed at t = 1.60 s and at t = 3.10 s.

b) Determine the average acceleration between t = 1.60 s and t = 3.10 s.

c) Determine the instantaneous acceleration at t = 1.60 s and t = 3.10 s.

for 1 a) you need to find \frac{dx}{dt} and put in your values for t
for 1 b) you need to use acceleration = (difference in)speed/(difference in)time with the answers you got from part a)
for 1 c) you need to find \frac{d^2x}{dt^2} and put in your values for t

Hope this helps, if you need any further help, feel free to ask!