A and B share a certain number of stamps, of which A accounts for (9/20). If B gives A 12 stamps, then B's remaining stamps account for (2/5) of the total. How many stamps do they share?
甲、乙两人共有邮票若干张，其中甲占(9/20)，若乙给甲12张，则乙余下的张数占总数的(2/5)．两人共有邮票多少张？
<gadget id="calculator">9 / 20</gadget>
<output>9/20 = around 0.45</output>

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

<gadget id="calculator">1 - (9/20) - (2/5)</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">12 / (3/20)</gadget>
<output>80</output>

<result>80</result>