Xiao Ming asked Mr. Liu how old his son is this year. Mr. Liu said: "Add 7 to the son's age, multiply 7, subtract 7, and finally divide by 7. The result is still 7." Please do the math, Mr. Liu's How old is your son?
小明问刘老师的儿子今年几岁，刘老师说："把儿子的年龄加上7再乘7再减去7，最后再除以7，其结果还是7．"请你算算，刘老师的儿子今年几岁？
<gadget id="calculator">7 * 7</gadget>
<output>49</output>

<gadget id="calculator">49 + 7</gadget>
<output>56</output>

<gadget id="calculator">56 / 7</gadget>
<output>8</output>

<gadget id="calculator">8 - 7</gadget>
<output>1</output>

<result>1</result>