It is known that the area of a trapezoid is 42 square centimeters, the sum of the upper and lower bases is 12 centimeters, what is the height of the trapezoid in centimeters.
已知一个梯形的面积是42平方厘米，上底与下底的和是12厘米，梯形的高是多少厘米．
<gadget id="calculator">2 / 12</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">42 * (1/6)</gadget>
<output>7</output>

<result>7</result>