The width of the H is 1/2 + 1 + 1/2 = 2 inches. Since the borders are the same on all sides, they are (4 -2)/2 = 1 inch wide all around. That means the height of the H is 5 -2*1 = 3 inches.
The area of the H is 2*(1/2*3) +(1/2*1) = 3 1/2 square inches.
The area of the overall painting is 4*5 = 20 square inches.
Then the fraction that is beige is
.. (20 -3.5)/20 = 16.5/20 = 82.5/100 = 82.5%
_____
Each of the actual dimensions is 6 times that shown in the calculation above. You could say we chose to factor out the 6s and cancel them in the ratio.