Respuesta :

BRAINST0RM
Since,
We have avg. acceleration it can be put in place of accelaration in the given time period.

v=15.3m/s
a= 3.95m/s
t= 2.25 s

by using,
a=(v-u)/t
3.95=(15.3-u)/2.25
(3.95*2.25)-15.3= -u
8.8875-15.3= -u
 -6.4125= -u
⇒ u= 6.4125 m/s