The school brought a batch of coal, burned all (2/3) less 1 ton in January, and burned the remaining (2/5) more than 1 ton in February, so there are still 4 tons left. How many tons is this batch of coal originally?
学校运来一批煤，一月份烧去全部的(2/3)少1吨，二月份烧去余下的(2/5)多1吨，这时还剩下4吨．这批煤原有多少吨？
<gadget id="calculator">4 + 1</gadget>
<output>5</output>

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

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">5 / (3/5)</gadget>
<output>25/3 = around 8.333333</output>

<gadget id="calculator">(25/3) - 1</gadget>
<output>22/3 = around 7.333333</output>

<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">1 - (2/3)</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">(22/3) / (1/3)</gadget>
<output>22</output>

<result>22</result>