Solve the equation: (3/4)x-(2/5)x=(7/30).
解方程：(3/4)x-(2/5)x=(7/30)．
<gadget id="calculator">7 / 30</gadget>
<output>7/30 = around 0.233333</output>

<gadget id="calculator">7 / 15</gadget>
<output>7/15 = around 0.466667</output>

<gadget id="calculator">(7/30) / (7/15)</gadget>
<output>1/2 = around 0.5</output>

<result>1/2 = around 0.5</result>