It costs 7.70 yuan to buy 2 pencil cases and 8 pencils, and 0.20 yuan to buy a pencil. How much is a pencil case?
买2个文具盒和8支铅笔要7.70元，一支铅笔0.20元，一个文具盒多少元？
<gadget id="calculator">8 * 0.2</gadget>
<output>1.6</output>

<gadget id="calculator">7.7 - 1.6</gadget>
<output>6.1</output>

<gadget id="calculator">6.1 / 2</gadget>
<output>3.05</output>

<result>3.05</result>