There are two tanks of goldfish. If 15 goldfishes are taken out from the first tank and put into the second tank, the goldfish in the second tank is exactly (5/7) of the first tank. It is known that there are 35 goldfishes in the second tank. How many goldfish were there in the first tank?
有两缸金鱼，如果从第一缸取出15尾放入第二缸，这时第二缸内的金鱼正好是第一缸的(5/7)，已知第二缸内原有金鱼35尾，第一缸内原有金鱼多少尾？
<gadget id="calculator">35 + 15</gadget>
<output>50</output>

<gadget id="calculator">5 / 7</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">50 / (5/7)</gadget>
<output>70</output>

<gadget id="calculator">70 + 15</gadget>
<output>85</output>

<result>85</result>