The 7 monkeys ate a total of 13 peaches, each big monkey ate 3 peaches, and each small monkey ate 1 peach. Please calculate how many big monkeys there are.
7只猴子一共吃了13个桃，每只大猴吃3个，每只小猴吃1个，请你算一算，大猴有多少只．
<gadget id="calculator">1 * 7</gadget>
<output>7</output>

<gadget id="calculator">13 - 7</gadget>
<output>6</output>

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

<gadget id="calculator">6 / 2</gadget>
<output>3</output>

<result>3</result>