The motion of a body is given by the equation dv(t)/dt=6.0-3v(t),where v(t) is speed in m/s and t in

The body doesn't have motion if it is at rest (if t=0) because v(t) is velocity and at rest there is not velocity.
dv(0)/d(0)=6-3v(0)
d(0)/d(0)=6-3(0)
0/0=6-0

0/0 is invalid
therefore there is no motion