Question: find a(t),v(t),s(t) from x=(-1+2t)m
Since this is a physics question, I am assuming that the m at the end of x=(-1+2t)m refers to metres.
s(t) is simply the distance travelled as a function of time and is what you have go started off with. i.e. x = s.
So. s(t) = -1 + 2t m
v(t) is the velocity, or speed, and is the time rate of change of distance.
i.e. v = ds/dt = d(-1+2t)/dt = 2
v(t) = 2 m/s -- this is a constant speed.
a(t) is the acceleration and this is the time rate of change of the velocity (speed).
Since the speed is constant, then the speed is not changing, so the acceleration is zero.
This can also be got by differentiating the speed wrt time.
i.e. a = dv/dt = 0
So, a(t) = 0 m/s^2