Xiao Ming reads an extra-curricular book and reads 30 pages. The number of pages he didn’t read is 30% less than the number of pages he read. How many pages are left unread?
小明看一本课外读物，看了30页，没看的比看了少30%，还有多少页没看？
<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 - (3/10)</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">30 * (7/10)</gadget>
<output>21</output>

<result>21</result>