Known: 3a+2x=50, a=12, then x=how much.
已知：3a+2x=50，a=12，则x=多少．
<gadget id="calculator">50 - 36</gadget>
<output>14</output>

<gadget id="calculator">14 / 2</gadget>
<output>7</output>

<result>7</result>