Answer
The instantaneous acceleration is the slope of the line $v=50+20t $which is found to be $20~m/s^2$.
Work Step by Step
From the graph, at $t=0$, $v=50$ and at $t=3$, $v=110$.
Using the slope formula which is for the line $v=50+20t$:
$m=\frac{110-50}{3-0}=20$
Thus, the instantaneous velocity is $20~m/s^2$.
