Solve the equation: 5(x-2)-4.2x=30.
解方程：5(x-2)-4.2x=30．
<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<gadget id="calculator">10 + 30</gadget>
<output>40</output>

<gadget id="calculator">5 - 4.2</gadget>
<output>0.8</output>

<gadget id="calculator">40 / 0.8</gadget>
<output>50</output>

<result>50</result>