4. Doraemon and Nobita are playing "Rock, Paper, Scissors," with the rule that the winner of each round gets two dorayaki, the loser gets no dorayaki, and if it's a tie, each gets one dorayaki. Nobita knows that Doraemon can only play rock, but he still wants to share dorayaki with Doraemon, so he decides to play scissors once every ten rounds and play rock several times. After 20 rounds, the dorayaki are all gone, and Nobita has 30 dorayaki. How many dorayaki did Doraemon get? $\qquad$
Analysis: [Enumeration Method] xrs played a total of 20 rounds, among which Doraemon played scissors 2 times, and lost both times, thus getting no dorayaki. In the remaining 18 rounds, he needs to win 12 times and draw 6 times to get 30 dorayaki, $2 \times 12 + 1 \times 6 = 30$ (pieces). From this, we can infer that Nobita won 2 times, drew 6 times, and lost 12 times, and the dorayaki he got is: $2 \times 2 + 1 \times 6 = 10$ (pieces)