Add 7 to a certain number, multiply by 5, and then subtract 9 to get 51. What is this number?
某数加7，乘以5，再减去9，得51，这个数是多少．
<gadget id="calculator">51 + 9</gadget>
<output>60</output>

<gadget id="calculator">60 / 5</gadget>
<output>12</output>

<gadget id="calculator">12 - 7</gadget>
<output>5</output>

<result>5</result>