There are two steel pipes, the first steel pipe is 54 meters long and the second steel pipe is 50 meters long. After two steel pipes use the same long section, the remaining length of the second steel pipe is (7/9) of the remaining length of the first steel pipe. How many meters is the length of the first steel pipe after a section is used?
有两根钢管，第一根钢管长54米，第二根钢管长50米．两根钢管使用同样长的一段后，第二根钢管剩下的长度是第一根钢管剩下的长度的(7/9)，用去一段后第一根钢管长多少米？
<gadget id="calculator">54 - 50</gadget>
<output>4</output>

<gadget id="calculator">7 / 9</gadget>
<output>7/9 = around 0.777778</output>

<gadget id="calculator">1 - (7/9)</gadget>
<output>2/9 = around 0.222222</output>

<gadget id="calculator">4 / (2/9)</gadget>
<output>18</output>

<result>18</result>