Question 1111318
Team A  {{{1/(t-6)}}}
Team B  {{{1/t}}}
A & B  {{{1/4}}}


{{{1/(t-6)+1/t=1/4}}}
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.
.
{{{t^2-14t+24=0}}}


{{{(t-2)(t-12)=0}}}


{{{highlight(t=12)}}}


Team A,  fix one car alone, 6 hours
Team B, fix one car alone, 12 hours



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check
{{{1/(12-6)+1/12}}}
{{{1/6+1/12}}}

{{{2/12+1/12}}}

{{{3/12=1/4}}},{{{check}}}{{{right}}}