There are two iron wires of equal length. The first wire takes up 10 meters and the second uses up 19 meters. The ratio of the first wire to the second wire is 4:1. How many meters are left on the first wire?
有两根等长的铁丝，第一根用去10米，第二根用去19米，余下的铁丝第一根和第二根的比是4：1，第一根铁丝剩下多少米？
<gadget id="calculator">19 - 10</gadget>
<output>9</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

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

<gadget id="calculator">9 / (3/4)</gadget>
<output>12</output>

<result>12</result>