To type a manuscript, Xiao Li typed (1/3) of all manuscripts per hour, which is less than (1/4) of all manuscripts per hour. How many hours did the two cooperate to finish typing.
打一份稿件，小李每小时打全部稿件的(1/3)，小于每小时打全部稿件的(1/4)，两人合作多少小时打完．
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(1/3) + (1/4)</gadget>
<output>7/12 = around 0.583333</output>

<gadget id="calculator">1 / (7/12)</gadget>
<output>12/7 = around 1.714286</output>

<result>12/7 = around 1.714286</result>