You have (140 mathrm{ft}) of fencing to enclose a rectangular region that borders a river. You do

Question:

You have $140 \mathrm{ft}$ of fencing to enclose a rectangular region that borders a river. You do not have to fence in the side that borders the river. The width is equal to $2 a$, and the length is equal to six times the width less 10 . Find the dimensions of the region to be fenced.

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