In the first three basketball games, Xiao Wang shot 30 times and hit 12 times. In the fourth game, he shot 10 times. To make the shooting rate of these four games rise to 50%, how many shots did he have to make in the fourth game? Second-rate.
在前三场篮球比赛中，小王共投篮30次，命中12次，在第四场比赛中，他投篮10次，要使这四场命中率上升为50%，他第四场要命中多少次．
<gadget id="calculator">30 + 10</gadget>
<output>40</output>

<gadget id="calculator">50 / 100</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">40 * (1/2)</gadget>
<output>20</output>

<gadget id="calculator">20 - 12</gadget>
<output>8</output>

<result>8</result>