Question:

The auction went 1NT-3NT by the opponents. We see the first trick. What will you play after the underlined card is played by dummy?

Vul: Dlr:	DUMMY K92
Opening Lead 6		YOU AJ83

Answer:

3. You can use a tool called the Rule of 11, which allows you to "read" a fourth-best lead. It works by subtracting the lead from 11 and you'll know how many cards higher than the lead are in the other three hands. 11-6=5. We can see all five cards higher than the 6 between our hand and dummy. That means declarer has no cards that beat partner's lead. Playing the 3 allows partner to continue this suit through dummy.