Solve the equation: (3+x): x=7: 4.
解方程：(3+x)：x=7：4．
<gadget id="calculator">7 / 4</gadget>
<output>7/4 = around 1.75</output>

<gadget id="calculator">(7/4) - 1</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">3 / (3/4)</gadget>
<output>4</output>

<result>4</result>