Multiply a certain number by 3, add 2, subtract 5, the difference is 12, what is this number?
某数乘以3，再加2，减去5，差是12，这个数是多少？
<gadget id="calculator">5 - 2</gadget>
<output>3</output>

<gadget id="calculator">12 + 3</gadget>
<output>15</output>

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

<result>5</result>