Question 1025133
Fred can paint a house in 12 hours and George 
can paint the same house in 14 hours. How long 
does it take Fred and George to paint the house 
together?
<pre>
Fred's painting rate 1 house per 12 hours plus 
George's rate of 1 house per 14 hours gives 
their combined rate as

1/12 + 1/14 = 7/84+6/84 = 13/84ths of a house 
per hour.  Let this equal to 1 house per x hours, 
so

1/x = 13/84

Taking reciprocals of both side

x = 84/13 = 6 6/13 hours.

Edwin</pre>