In order to find the perimeter, all we have to do is add all three of the sides:
x^2 + 3 + 2x + 5 + 2x = 29
x^2 + 4x + 8 = 29
Subtract 29 from both sides:
x^2 + 4x - 21 = 0
Factor:
(x + 7)(x - 3) = 0
{-7, 3}
3 can be the only possible length, since a length can't be a negative number.
2x = 6
2x + 5 = 11
x^2 + 3 = 12
-T.B.
