A velocity vs time graph what is the acceleration of the object

If the object is moving with an acceleration of + 4 m/s/s (i. e., changing its velocity by 4 m/s per second), then the slope of the line will be + 4 m/s/s.

The graph is missing, but ill try to answer this anyway.

The acceleration is the rate of change of the velocity; this means that if you know the velocity as a function of time; v (t), you can obtain the acceleration a (t) by differentiate v (t) with respect to time; this is:

a (t) = dv (t) / dt

Them if you have a graph of velocity versus time, you can find the equation of v (t) and then find the acceleration.

For example, if your graph of velocity vs time is a linear relation, then the acceleration will be the slope of the linear relation.