A pile of coal burns 15% of the total amount in the first week, and 25% of the total amount in the second week. The amount of coal burned in the first week is 4.5 tons more than that in the second week. How many tons of coal are there in this pile?
一堆煤，第一周烧了总量的15%，第二周烧了总量的25%，第一周比第二周多烧煤4.5吨，这堆煤共有多少吨？
<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">15 / 100</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">(1/4) - (3/20)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">4.5 / (1/10)</gadget>
<output>45</output>

<result>45</result>