Students from three classes in grade six donated books to primary schools in mountainous areas. Class 2 donated as many books as Class 1 (5/6), and Class 3 donated less than Class 2 (1/5). Class 1 and Class 3 donated 180 books in total. So how many books were donated by these three classes?
六年级三个班学生给山区的小学捐献图书．二班捐献的书本数是一班的(5/6)，三班捐献的比二班少(1/5)，一班和三班共捐献图书180本．那么这三个班共捐献图书多少本．
<gadget id="calculator">5 / 6</gadget>
<output>5/6 = around 0.833333</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(5/6) * (4/5)</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">1 + (2/3)</gadget>
<output>5/3 = around 1.666667</output>

<gadget id="calculator">180 / (5/3)</gadget>
<output>108</output>

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

<gadget id="calculator">1 + (5/6) + (2/3)</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">108 * (5/2)</gadget>
<output>270</output>

<result>270</result>