A total of 750 tickets were sold for the football match and a total of 22,200 yuan was obtained. It is known that A-class tickets are 60 yuan each, B-class tickets are 30 yuan each, and C-class tickets are 18 yuan each. Among them, the number of C-class tickets is twice the number of B-class tickets. How many first-class tickets are there?
足球赛共出售750张票得22200元．已知甲等票每张60元，乙等票每张30元，丙等票每张18元．其中丙等票张数是乙等票张数的2倍．问其中甲等票有多少张？
<gadget id="calculator">60 * 750</gadget>
<output>45_000</output>

<gadget id="calculator">45_000 - 22_200</gadget>
<output>22_800</output>

<gadget id="calculator">60 * 2</gadget>
<output>120</output>

<gadget id="calculator">18 * 2</gadget>
<output>36</output>

<gadget id="calculator">120 - 30 - 36</gadget>
<output>54</output>

<gadget id="calculator">60 + 54</gadget>
<output>114</output>

<gadget id="calculator">22_800 / 114</gadget>
<output>200</output>

<gadget id="calculator">200 * 2</gadget>
<output>400</output>

<gadget id="calculator">750 - 200 - 400</gadget>
<output>150</output>

<result>150</result>