If 10 similar cubes are arranged in a row, the surface area is reduced by 90dm**2, what is the surface area of each small cube?
把10个同样的正方体排成一排，表面积减少90dm**2，每个小正方体的表面积是多少．
<gadget id="calculator">10 - 1</gadget>
<output>9</output>

<gadget id="calculator">9 * 2</gadget>
<output>18</output>

<gadget id="calculator">90 / 18</gadget>
<output>5</output>

<gadget id="calculator">5 * 6</gadget>
<output>30</output>

<result>30</result>