Solve the equation: 3.5: x=5: 4.2.
解方程：3.5：x=5：4.2．
<gadget id="calculator">3.5 * 4.2</gadget>
<output>14.7</output>

<gadget id="calculator">14.7 / 5</gadget>
<output>2.94</output>

<result>2.94</result>