



 
Hi David, Suppose the length of a rectangle in the set is $L$ units and its width is $W$ units. The fact that the length is inversely proportional to the width means that there is a constant $k$ so that \[L = \frac{k}{W}.\] The fact that $k$ is a constant means that the expression above is valid for each rectangle in the set with the same value of $k.$ You know that one of the rectangles has length $L = 12$ units and width $W = 6$ units means that \[12 = \frac{k}{6}.\] Solve this equation for $k.$ Another rectangle in the set has length $L = 9$ units and unknown width $W$ units. Substitute $L = 9$ and $k$ the value you just found into \[L = \frac{k}{W}.\] and solve for $W.$ Penny  


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