The school has 90 basketballs and volleyballs. There are 6 fewer basketballs than volleyballs. How many basketballs are there?
学校有篮球和排球共90个，篮球比排球少6个，篮球有多少个．
<gadget id="calculator">90 - 6</gadget>
<output>84</output>

<gadget id="calculator">84 / 2</gadget>
<output>42</output>

<result>42</result>