Li Xiaoming conducted 5 rounds of shooting practice, and the average number of shots in each round was 18. If he continues to conduct 2 more rounds of shooting practice, so that the average number of shots in these 7 rounds of shooting practice is not less than 20, how many shots must he make at least in these two rounds of practice.
李小明进行了5轮投篮练习，每轮投中的平均数是18个．如果他再继续进行2轮投篮练习，使这7轮投篮练习中，投中的平均数不低于20个，这两轮练习中，他至少要投中多少个．
<gadget id="calculator">20 * 7</gadget>
<output>140</output>

<gadget id="calculator">18 * 5</gadget>
<output>90</output>

<gadget id="calculator">140 - 90</gadget>
<output>50</output>

<result>50</result>