There is a pile of coal, after being transported out (4/9), 210 tons are transported in again. At this time, the amount of coal stored is the original (3/4). How many tons of coal was there?
有一堆煤，运出(4/9)后，又运进210吨．这时的存煤量是原来的(3/4)．原来有煤多少吨？
<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">4 / 9</gadget>
<output>4/9 = around 0.444444</output>

<gadget id="calculator">1 - (4/9)</gadget>
<output>5/9 = around 0.555556</output>

<gadget id="calculator">(3/4) - (5/9)</gadget>
<output>7/36 = around 0.194444</output>

<gadget id="calculator">210 / (7/36)</gadget>
<output>1_080</output>

<result>1_080</result>