The school organizes a cultural performance. Dongdong's seat is the 7th from the left and the 10th from the right. How many seats are there in this row?
学校组织看文艺表演，东东的座位从左数是第7个，从右数是第10个，这一行有多少个座位？
<gadget id="calculator">10 - 1</gadget>
<output>9</output>

<gadget id="calculator">7 + 9</gadget>
<output>16</output>

<result>16</result>