The two bags of grain weigh 81 kg in total. The first bag is eaten (2/5), and the second bag is eaten (3/4), leaving a total of 29 kg. What is the weight of the first bag of grain?
两袋粮食共重81千克，第一袋吃去了(2/5)，第二袋吃去了(3/4)，共余下29千克，原来第一袋粮食重多少千克．
<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">81 * (3/4)</gadget>
<output>243/4 = around 60.75</output>

<gadget id="calculator">29 - 81</gadget>
<output>-52</output>

<gadget id="calculator">(243/4) + (-52)</gadget>
<output>35/4 = around 8.75</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(3/4) - (2/5) - 1</gadget>
<output>-13/20 = around -0.65</output>

<gadget id="calculator">1 + (-13/20)</gadget>
<output>7/20 = around 0.35</output>

<gadget id="calculator">(35/4) / (7/20)</gadget>
<output>25</output>

<result>25</result>