The perimeter of a polygon is the sum of the lengths of all its sides. A rectangle has 4 sides, and opposite sides are congruent, so 2 sides have length x + 5, and 2 sides have length 11. Add all the lengths and set the sum equal to 50. Then solve the equation for x.
x + 5 + x + 5 + 11 + 11 = 50
2x + 32 = 50
2x = 18
x = 9
Answer: x = 9
