When a number is divided by 7, the quotient is 3 and the remainder is 1. What is the number?
一个数除以7，商是3，余数是1，这个数是多少．
<gadget id="calculator">3 * 7</gadget>
<output>21</output>

<gadget id="calculator">21 + 1</gadget>
<output>22</output>

<result>22</result>