t = t
u = 12
a = -5 (the minus sign is important)
Multiply through by 2 to clear the fraction and rearrange into the form
Solve using your favourite method, this one does factorise
To find the value find v at the given time
Since it implies that the particle is now moving in the negative direction, back towards the origin. Therefore it follows that t = 0.8 is correct.
oops, just saw that the question asks for the values of t (implying more than one solution) so if you quote both you should be correct and can disregard the stuff about v