Xiao Ming went to the supermarket to buy a pencil case and spent 15 yuan, which was 2.9 yuan more than buying pencils. How much did Xiao Ming spend on the pencil?
小明去超市买文具盒花了15元，比买铅笔多花了2.9元．小明买铅笔花了多少钱？
<gadget id="calculator">15 - 2.9</gadget>
<output>12.1</output>

<result>12.1</result>