The length of the surrounding fence is equal to the perimeter of the garden. That is the sum of the lengths of the straight sides and the curved arc. The arc length is given by the formula ...
s = r·θ . . . . . where θ is the central angle in radians
There are π radians in 180°, so the arc will have a measure in radians of ...
θ = 132° × (π/180°) = 11/15π ≈ 2.3038 . . . . radians
Then the length of the curved side of the garden is ...
s = (50 ft)(2.3038 radian) ≈ 115.2 ft
The fence length is the sum of the arc length and the two radii:
perimeter = 115.2 ft + 2×50 ft = 215.2 ft
About 215 feet of fencing are needed to enclose the garden.