What is 1/3+a=5/4 and what does it mean

this is the answe but i dont know what it means

  180 ft

Step-by-step explanation:

The perimeter of a geometric figure is the sum of the lengths of its sides. Opposite sides of a rectangle are of equal length, so the perimeter can be figured as twice the sum of the length of adjacent sides:

  2(60 ft + 30 ft) = 180 ft

Mrs. Chen needs 180 feet of fence.