Kinematics of motion in a straight line — practice question

Particles $P$ and $Q$ are launched vertically upwards from level ground at the same moment. Their initial speeds are $12\,\text{m s}^{-1}$ and $7\,\text{m s}^{-1}$ respectively, and $t$ seconds after launch their heights above the ground are $h_P$ and $h_Q$ respectively. On the way back down to the ground, each particle comes to rest.