Answer:


Step-by-step explanation:
Perimeter = 2(Length + Width)
In short form:
P = 2l + 2w
Here make "l" the subject:

relocate term w

dividing both sides by 2

Now find the length of picture frame:
Given: P = 84 inches, W = 16 inches

evaluate

Hence, the length of the picture frame is 26 inches.