Solve the equation: 30x+45*(30-x)=1224.
解方程：30x+45*(30-x)=1224．
<gadget id="calculator">45 * 30</gadget>
<output>1_350</output>

<gadget id="calculator">1_350 - 1_224</gadget>
<output>126</output>

<gadget id="calculator">45 - 30</gadget>
<output>15</output>

<gadget id="calculator">126 / 15</gadget>
<output>42/5 = around 8.4</output>

<result>42/5 = around 8.4</result>