The mother duck took 10 ducklings to swim in the small river. After a while, 4 ducklings landed on the shore; after a while, 2 more ducklings came. How many ducks are left in the river at this time?
鸭妈妈带着10只小鸭在小河里游泳，一会儿，4只小鸭上了岸；过了一会儿，又来了2只小鸭子．这时河里还剩下多少只鸭子？
<gadget id="calculator">10 - 4</gadget>
<output>6</output>

<gadget id="calculator">6 + 2 + 1</gadget>
<output>9</output>

<result>9</result>