birthday cake, each piece cut into five equal parts weighs 80 grams more than each piece cut into seven equal parts, how many grams does this birthday cake weigh?
一个生日蛋糕，切成五等份的每一块比切成七等份的每一块重80克，这个生日蛋糕重多少克？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">(1/5) - (1/7)</gadget>
<output>2/35 = around 0.057143</output>

<gadget id="calculator">80 / (2/35)</gadget>
<output>1_400</output>

<result>1_400</result>