let length of painting = L
and width = W
from area = length times width
180 inch^2 = L times W
but L = 5/4 times W
180 inch^2 = 5/4 times W times W
W^2 = (4 x 180)/5
W = 12
but L = 5/4 x W
L = 5/4 x 12
L = 15
Answer: The dimensions of the painting are 12 x 15 inches.