I have attempted this question in so many different ways but I am getting nowhere. Could someone point me in the correct direction so I can work it out myself?
Here is the question:
An object $K$ is shot upwards with a velocity $v_i$, after $t$ seconds it is 50 metres high and time $2t$ seconds it is 80 metres high. Solve for $v_i$ and $t$.
I have tried breaking it into two parts but I always hit a wall.