The sixth grade launched a book donation activity. The number of books donated by Class Six 1 accounted for 30% of the total book donations, and the number of books donated by Class Six 2 accounted for 35% of the total book donations. Class Six 1 donated 15 books less than Class Six 2. How many books were donated in total?
六年级开展了捐书活动，六1班捐书的本数占捐书总数的30%，六2班捐书的数占捐书总数的35%，六1班比六2班少捐15本，这次活动共捐书多少本？
<gadget id="calculator">35 / 100</gadget>
<output>7/20 = around 0.35</output>

<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">(7/20) - (3/10)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">15 / (1/20)</gadget>
<output>300</output>

<result>300</result>