Question
Ian and Billy take 6 days to assemble a toy house. Billy and Mark take 3 days to build the same house while Ian and Mark take only 5 days. How many complete days would the three of them take to build the same toy house?
4 m

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Ian and Billy take 6 days to assemble a toy house. Billy and Mark take 3 days to build the same house while Ian and Mark take only 5 days. How many complete days would the three of them take to build the same toy house?