



 
Hi Kenneth, You let $c$ be the number of carpenters, $d$ the number of days and $h$ the number of houses and developed the equation \[h = k \times c \times d \mbox{ where $k$ is a constant.}\] You then used the information given in the problem to show that $k = \large \frac15$ so that \[h = \frac { c \times d}{5}. \] The question " How many carpenters can build 6 houses in 15 days?" can then be answered by substituting $h = 6$ and $d = 15$ into the equation above and solving for $c.$ You can similarly answer "2 carpenters can build 6 houses in how many days?" by substituting$c = 2$ and $h = 6$ into the equation and solving for $d.$ I hope this helps,  


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