Seventh-grade student collected stamps, Hong Hong collected 90 stamps, 20% more than Ming Ming, and Ming Ming collected 50% less than Lan Lan, how many stamps did Lan Lan collect?
七年级同学集邮，红红收集了90张，比明明多收集了20%，明明又比兰兰少收集了50%，兰兰收集了多少张邮票？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 + (1/5)</gadget>
<output>6/5 = around 1.2</output>

<gadget id="calculator">50 / 100</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 - (1/2)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">90 / (6/5) / (1/2)</gadget>
<output>150</output>

<result>150</result>