If the number of paper cranes remains the same, how many frogs need to be increased or decreased to make the number of frogs seven times the number of paper cranes?
千纸鹤的数量不变，要使青蛙的只数是千纸鹤只数的7倍，需要增加或减少多少只青蛙？
<gadget id="calculator">6 * 7</gadget>
<output>42</output>

<gadget id="calculator">42 - 40</gadget>
<output>2</output>

<result>2</result>