You can go for any valid trio for your last 3 tile match and any valid duo for your 2 tile match as long as your other 3 trio matches are a 3 color straight.
Ex. 2,3,4 | 2,3,4 | 2,3,4 | ?,?,? | ?,?
So, the question mark tiles above can be anything as long as they are a legit pair or trio.