Check the rules of the World Cup European qualifiers play-offs

The scores of the two rounds are the same. Look at the away goal difference. If the scores of the two teams are still the same as the away goal difference 90 minutes after the second game, overtime will be played. The rule of overtime is that if both sides score goals, the visiting team wins. This is also an away goal. If there is still no result, there will be a penalty shootout.