The small owner paid 37.8 yuan for water in October, which is 4.2 yuan less than that in September. How much is the water fee for September? (column equation solution)
小东家十月份付水费37.8元，比九月份少付4.2元，九月份付水费多少元？(列方程解答)
<gadget id="calculator">4.2 + 37.8</gadget>
<output>42</output>

<result>42</result>