There is an alloy made of three metals, copper, tin, and zinc. Among them, steel and zinc each account for the total weight (9/25), what percentage of the total weight is tin?
有一块合金由铜、锡、锌三种金属熔合而成．其中钢和锌各占总重量的(9/25)，锡占总重量的几分之几？
<gadget id="calculator">9 / 25</gadget>
<output>9/25 = around 0.36</output>

<gadget id="calculator">1 - (9/25) - (9/25)</gadget>
<output>7/25 = around 0.28</output>

<result>7/25 = around 0.28</result>