The area of a terraced field is 90 square meters, the upper base is 7 meters, and the lower base is 11 meters. How many meters is it high?
一块梯形田的面积是90平方米，上底是7米，下底是11米，它的高是几米？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">7 * (1/2)</gadget>
<output>7/2 = around 3.5</output>

<gadget id="calculator">11 * (1/2)</gadget>
<output>11/2 = around 5.5</output>

<gadget id="calculator">(7/2) + (11/2)</gadget>
<output>9</output>

<gadget id="calculator">90 / 9</gadget>
<output>10</output>

<result>10</result>