The school bought 60 volleyballs, and the basketballs it bought are half of the volleyballs. How many two kinds of balls did they buy? what is the formula
学校买来排球60只，买来的篮球是排球的一半，两种球共买多少只？算式是多少
<gadget id="calculator">60 / 2</gadget>
<output>30</output>

<gadget id="calculator">60 + 30</gadget>
<output>90</output>

<result>90</result>