In a subtraction formula, the minuend is 6 times the subtrahend, the known difference is 15, what is the subtrahend?
在一道减法算式里，被减数是减数的6倍，已知差是15，减数是多少？
<gadget id="calculator">6 - 1</gadget>
<output>5</output>

<gadget id="calculator">15 / 5</gadget>
<output>3</output>

<result>3</result>