We're gonna call x the length of the shortest side. The medium side is 3 longer than the shorter side, and the longest side is 14 longer than the shortest (11 + 3 = 14):
Perimeter = shortest side + medium side + longest side
59 = (x) + (x + 3) + (x + 14)
59 = 3x + 17
3x = 42
x = 14
Shortest side = 14
Medium side = 17
Longest side = 28