The difference between the volumes of cubes A and B is 21 cubic centimeters, and the length of side A is (1/2) the length of side B. What is the volume of cube A in cubic centimeters?
甲、乙两个正方体的体积差是21立方厘米，甲棱长是乙棱长的(1/2)，那么甲正方体的体积是多少立方厘米？
<gadget id="calculator">8 / 1</gadget>
<output>8</output>

<gadget id="calculator">8 - 1</gadget>
<output>7</output>

<gadget id="calculator">21 / 7</gadget>
<output>3</output>

<result>3</result>