Question 666104
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Hi,
A painter can paint a certain house in 12 hours by herself: 
In 5hrs {{{5/12}}} done.  {{{7/12}}} of the house remaining to complete
helper 15 hours to do the same job himself:
  {{{1/12 + 1/15}}} = 9/60  of the house per hour together
{{{(7/12)/(9/60)}}} = 35/9 hr   remaining time together