Add a 0 after a one-digit number to become a two-digit number. This two-digit number is 63 more than the original one-digit number. What is the original one-digit number?
一个一位数后面添写一个0，成为一个两位数，这个两位数比原来的一位数多63，原来的一位数是多少．
<gadget id="calculator">10 - 1</gadget>
<output>9</output>

<gadget id="calculator">63 / 9</gadget>
<output>7</output>

<result>7</result>