Solve the equation: 3(x+4)=63.
解方程：3(x+4)=63．
<gadget id="calculator">3 * 4</gadget>
<output>12</output>

<gadget id="calculator">63 - 12</gadget>
<output>51</output>

<gadget id="calculator">51 / 3</gadget>
<output>17</output>

<result>17</result>