Question 1184930
At t=0 the speed was 4.0 and at t=10, the speed is 12 (m/sec)
But the speed changed over time, in this case linear.
The displacement is speed*time, so it is the average (for a linear function), which is 8 m/sec, multiplied by the total time (10 sec), or 80 m (note the units).
This is also the same formula for area of a trapezoid ((1/2) h (b1+b2))
the last distance goes from 12 m/sec to 0, but it is linear and over those 2 seconds, it is the average of those two values* the time of 2 seconds.