After a bag of flour is used (7/10), buy back 25kg and put it in it. At this time, the quality of the flour in the bag is exactly equal to (4/5) the weight of the original bag of flour. How many kilograms of flour does this bag have? (Solution of column equation)
一袋面粉用去(7/10)后，又买回25kg放入其中，这时袋中的面粉质量正好相当于原来那袋面粉质量的(4/5)，这袋面粉原来有多少千克？(列方程解)
<gadget id="calculator">7 / 10</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(4/5) - 1</gadget>
<output>-1/5 = around -0.2</output>

<gadget id="calculator">(7/10) + (-1/5)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">25 / (1/2)</gadget>
<output>50</output>

<result>50</result>