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) = 23 x + x + (2x – 5) = 23 x + x + (2x + 5) = 23 x + (2x – 5) + (2x – 5) = 23