Xiaojun bought a total of 15 stamps with a face value of 80 cents and 1 yuan, and spent a total of 13.6 yuan. How many stamps with a face value of 80 cents did Xiaojun buy?
小军买了面值为80分和1元的邮票共15枚，共花了13.6元，则小军买了面值为80分的邮票多少枚．
<gadget id="calculator">1 * 15</gadget>
<output>15</output>

<gadget id="calculator">15 - 13.6</gadget>
<output>1.4</output>

<gadget id="calculator">1 - 0.8</gadget>
<output>0.2</output>

<gadget id="calculator">1.4 / 0.2</gadget>
<output>7</output>

<result>7</result>