The weight of 4 elephants is 18 tons, and the weight of 15 cows is 9 tons. On average, how much is each elephant heavier than each cow?
4头大象的体重是18吨，15头牛的体重是9吨，平均每头大象比每头牛重多少千克？
<gadget id="calculator">18 / 4</gadget>
<output>9/2 = around 4.5</output>

<gadget id="calculator">9 / 15</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(9/2) - (3/5)</gadget>
<output>39/10 = around 3.9</output>

<gadget id="calculator">(39/10) * 1_000</gadget>
<output>3_900</output>

<result>3_900</result>