s = 8 (because we've gone from 0 to 8 on the line)

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