The third side is described in relation to one of the equal sides, so let x = the length of one of the equal sides. Which equation models the problem?x + x + (5 – 2x) = 23x + x + (2x – 5) = 23x + x + (2x + 5) = 23x + (2x – 5) + (2x – 5) = 23

The two equal sides each have length x, so together they contribute x + x. The third side is 5 less than twice the length of one equal side, so its length is 2x − 5. Since the perimeter is 23, the equation is x + x + (2x − 5) = 23, which is choice B.

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