In basketball, a shot inside the 3-point line is worth 2 points, and a shot outside the 3-point line is worth 3 points. In a game, Xiaohong made a total of 9 balls and scored 20 points. How many 2-pointers did she make?
篮球比赛中，3分线内投中一个球得2分，3分线外投中一个球得3分．在一场比赛中，小红一共投中了9个球，得20分，她投中了多少个2分球．
<gadget id="calculator">3 * 9</gadget>
<output>27</output>

<gadget id="calculator">27 - 20</gadget>
<output>7</output>

<gadget id="calculator">3 - 2</gadget>
<output>1</output>

<gadget id="calculator">7 / 1</gadget>
<output>7</output>

<result>7</result>