Are you able to help me to simplify this?

$\displaystyle \Pi_t = 0.5 \Pi_t + 0.5 \Pi_{t-1} - 1.5(u_t-u_n) $

Im finding it quite difficult, what i have so far is this.

$\displaystyle 0.5\Pi_t=0.5\Pi_{t-1}-1.5(u_t-u_n)$

Im not sure if thats right. I need it in terms of $\displaystyle \Pi_t$

Preferably in a full unit of it.

Thanks.