Answer:
3 inches
Step-by-step explanation:
Lenght = 18 inches
Width =15 inches
Perimeter of the rectangular painting and frame = 90 inches
Let X be the width of the frame
The width of the framed picture = 15 + 2x
The length of the framed picture = 18 + 2x
Perimeter = 2 (L + W)
90 = 2(15 + 2x + 18+ 2x)
90 = 2(33 + 4x)
90 = 66 + 8x
8x = 90 - 66
8x = 24
x = 24/8
x = 3 inches
the width of the frame is 3 inches
