A tourist attraction has two types of tickets for children and adults. The price of a child ticket is 20 yuan, and the price of an adult ticket is 40 yuan. A tourist group consisting of 9 families (each family consists of two adults, or two adults and one child) travels to this scenic spot. If they buy a group ticket and spend 120 yuan less than each individual ticket, then the How many people are there in the tour group?
某旅游景点有儿童、成人两种规格的门票，儿童票的价格为20元，成人票的价格为40元，如果是团体购票，不论儿童还是成人，每人均30元．一个由9个家庭组成的旅游团(每个家庭由两位大人，或两个大人、一个小孩组成)来此景点旅游，如果他们买团体票比各自单独买票少花120元，那么，这个旅游团一共有多少人？
<gadget id="calculator">40 * 2 * 9</gadget>
<output>720</output>

<gadget id="calculator">30 * 2 * 9</gadget>
<output>540</output>

<gadget id="calculator">720 - 540 - 120</gadget>
<output>60</output>

<gadget id="calculator">30 - 20</gadget>
<output>10</output>

<gadget id="calculator">60 / 10</gadget>
<output>6</output>

<gadget id="calculator">6 * 3</gadget>
<output>18</output>

<gadget id="calculator">9 - 6</gadget>
<output>3</output>

<gadget id="calculator">3 * 2</gadget>
<output>6</output>

<gadget id="calculator">18 + 6</gadget>
<output>24</output>

<result>24</result>