What is a comprehensive formula composed of 120-30=90, 18+12=30, 90/30=3.
由120-30=90，18+12=30，90/30=3组成一道综合算式是多少．
<gadget id="calculator">18 + 12</gadget>
<output>30</output>

<gadget id="calculator">120 - 30</gadget>
<output>90</output>

<gadget id="calculator">90 / 30</gadget>
<output>3</output>

<result>3</result>