Mom bought two bags of flour, the weight of the first bag was 2/3 of the weight of the second bag, after a while, 21 kg was eaten in the first bag, and 5/8 in the second bag, The weight of the remaining flour in the two bags is equal, how much is the original flour in the second bag? (Solution of column equation)
妈妈买来两袋面粉，第一袋的重量是第二袋重量的(2/3)，过了些日子，第一袋吃掉了21千克，第二袋吃掉了(5/8)，两袋剩下的面粉重量相等，第二袋原有面粉多少千克？(列方程解)
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">5 / 8</gadget>
<output>5/8 = around 0.625</output>

<gadget id="calculator">(5/8) - 1</gadget>
<output>-3/8 = around -0.375</output>

<gadget id="calculator">(2/3) + (-3/8)</gadget>
<output>7/24 = around 0.291667</output>

<gadget id="calculator">21 / (7/24)</gadget>
<output>72</output>

<result>72</result>