The quotient of 5.4 divided by 3, plus the product of a certain number and 0.4, the sum is 4.2. Ask for a certain number. (column equation)
5.4除以3的商，加上某数与0.4的积，和是4.2．求某数．(列方程)
<gadget id="calculator">5.4 / 3</gadget>
<output>1.8</output>

<gadget id="calculator">4.2 - 1.8</gadget>
<output>2.4</output>

<gadget id="calculator">2.4 / 0.4</gadget>
<output>6</output>

<result>6</result>