A motorcyclist traveling at 72 km / h slowed down to 54 km / h in a delta t = 25c. What is the motorcyclist’s acceleration

A motorcyclist traveling at 72 km / h slowed down to 54 km / h in a delta t = 25c. What is the motorcyclist’s acceleration and how is it directed relative to speed?

Let’s translate into SI:
72km / h = 20m / s – initial speed V
54km / h = 15m / s – final speed Vo
The speed of the motorcyclist V = Vo – at, whence the acceleration (the formula can be used without derivation):
a = (Vо – V) / t
a = (20 – 15) / 25 = 0.2 (m / s ^ 2)
The acceleration vector is directed in the direction opposite to the direction of the velocity vector.
Answer: a = 0.2 (m / s ^ 2)
The acceleration vector is directed in the direction opposite to the direction of the velocity vector.