Class 1 of the sixth grade is preparing to hold a graduation party. Xiaojun and Xiaoqiang are responsible for decorating the classroom. If two people hang the color bar together, it can be finished in 8 minutes; if Xiaojun completes it alone, it will take 12 minutes. If two people set up tables and chairs together, it can be done in 15 minutes; Xiaoqiang can finish it alone, and the group can finish it in 20 minutes. How many minutes will it take for two people to complete these two tasks together?
六年级1班准备召开毕业联欢会，小军和小强负责布置教室．若两人一起挂彩条，8分钟可以挂完；小军单独完成，则需12分钟．若两人一起摆桌椅，15分钟可以摆完；小强单独完成，则组20分钟完成．两人共同完成这两项工作，最短需要多少分钟．
<gadget id="calculator">12 / 1</gadget>
<output>12</output>

<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/20) * 12</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 - (3/5)</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(2/5) / (1/15)</gadget>
<output>6</output>

<gadget id="calculator">12 + 6</gadget>
<output>18</output>

<result>18</result>