Answer:
![-4 m/s^2](https://tex.z-dn.net/?f=-4%20m%2Fs%5E2)
Explanation:
The acceleration of the bycicle is given by:
![a=\frac{v-u}{t}](https://tex.z-dn.net/?f=a%3D%5Cfrac%7Bv-u%7D%7Bt%7D)
where
v = 20 m/s is the final velocity of the bike
u = 40 m/s is the initial velocity
t = 5 s is the time interval
Substituting numbers, we find
![a=\frac{20 m/s-40 m/s}{5s}=-4 m/s^2](https://tex.z-dn.net/?f=a%3D%5Cfrac%7B20%20m%2Fs-40%20m%2Fs%7D%7B5s%7D%3D-4%20m%2Fs%5E2)
and the acceleration is negative, which means that the bycicle is slowing down.
I believe it is -1.11 m/s^2. I will let you know if its correct