Xiao Ming just bought a pair of triangular rulers and 2 rulers with 10 yuan; Li Hua bought a pair of the same triangle ruler and 1 pair of rulers with 10 yuan, and got back 1 yuan. How much is a pair of triangle rulers?
小明拿10元钱正好买了1副三角尺和2把直尺；李华拿10元钱买了1副同样的三角尺和1把同样的直尺，找回1元钱．一副三角尺多少钱？
<gadget id="calculator">10 - 9</gadget>
<output>1</output>

<gadget id="calculator">1 * 2</gadget>
<output>2</output>

<gadget id="calculator">10 - 2</gadget>
<output>8</output>

<result>8</result>