Type A sugar is 8.40 yuan per kilogram, and type B sugar is 7.12 yuan per kilogram. After mixing 5 kilograms of sugar B with several kilograms of sugar A, the average sugar per kilogram is 7.60 yuan. How many kilograms of sugar A are used?
甲种糖每千克8.40元，乙种糖每千克7.12元，用5千克乙种糖和若干千克甲种糖混合后，平均每千克糖是7.60元，甲种糖用了多少千克？
<gadget id="calculator">5 * 7.6</gadget>
<output>38</output>

<gadget id="calculator">7.12 * 5</gadget>
<output>35.6</output>

<gadget id="calculator">38 - 35.6</gadget>
<output>2.4</output>

<gadget id="calculator">8.4 - 7.6</gadget>
<output>0.8</output>

<gadget id="calculator">2.4 / 0.8</gadget>
<output>3</output>

<result>3</result>