Tracy and Dave together complete the task in hours
Given Tracy alone take 8 hours to complete work and dave alone take 12 hours to complete the work.
Let's say together they worked in x hours
⇒in 1 hour they worked th part of the work
Tracy herself worked 8 hours to complete the whole task
⇒ in 1 hour Tracy completes th part of the task
Dave himself worked 8 hours to complete the whole task
⇒ in 1 hour Dave completes th part of the task
By proportions
⇒+
=
{ using operation addition}
⇒ x=
Therefore,Tracy and Dave together complete the task in hours
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