This is a test of commonsense. Complete the next sentence:

How to play a tennis tiebreaker
Decide who goes first.
The person who was set to serve at the end of the last game will serve first in the tiebreaker. In tennis, the server switches at the end of every game.
If you were the receiver in the game before the tiebreaker, then you will serve first. Just like in a normal tennis game, the first service will be from the deuce (right) side of the of the hash.