The base of the picture is 16 inches, when you add the frame there is an additional "x"
Base = 16 + x
The height of the picture is 20 inches, when you add the frame there is an additional "x".
Base = 20 + x
Perimeter = 2(base) + 2(height)
= 2(16 + x) + 2(20 + x)
= 32 + 2x + 40 + 2x
= 72 + 4x
Answer: (72 + 4x) inches