In order to caculate the perimeter of the given polygon, you first determine the length of each side of the polygon, just as follow:
side RS = 2 - (-2) = 2 + 2 = 4
side ST = 1 - (-3) = 1 + 4 = 5
side TQ = 2 - (-2) = 2 + 2 = 4
side QR = 1 - (-3) = 1 + 4 = 5
finally you sume all lengths:
4 + 5 + 4 + 5 = 18
Hence, the perimeters of the given polygon is 18 units