Type A sugar is 6 yuan per kilogram, and type B sugar is 8 yuan per kilogram. If you mix 5 kilograms of type A sugar with how many kilograms of type B sugar, you can get 7.8 yuan per kilogram of sugar.
甲种糖每千克6元，乙种糖每千克8元，把5千克甲种糖和多少千克乙种糖混在一起，就可得到每千克7.8元的糖．
<gadget id="calculator">5 * 7.8</gadget>
<output>39</output>

<gadget id="calculator">6 * 5</gadget>
<output>30</output>

<gadget id="calculator">39 - 30</gadget>
<output>9</output>

<gadget id="calculator">8 - 7.8</gadget>
<output>0.2</output>

<gadget id="calculator">9 / 0.2</gadget>
<output>45</output>

<result>45</result>