My grandma’s house used 8 tons of water last month, and I paid a water fee of 20 yuan; my grandma’s house used 12 tons of water last month, how much should I pay for water? (Solve with ratio)
奶奶家上个月用了8吨水，交了20元水费；姥姥家上个月用了12吨水，应该交水费多少元？(用比例解)
<gadget id="calculator">20 / 8</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">(5/2) * 12</gadget>
<output>30</output>

<result>30</result>