The expression which represents the missing side length is 6x - 20.
What expression represents the missing side length?
The perimeter of a figure is the sum of all its sides.
Let
The missing side length = y
So,
(3x - 4) + 2x + 2x + (3x - 4) = (2x + 6) + (2x + 6) + y
3x - 4 + 2x + 2x + 3x - 4 = 2x + 6 + 2x + 6 + y = 0
Make y the subject
3x - 4 + 2x + 2x + 3x - 4 - 2x - 6 - 2x - 6 = y
y = 6x - 20
Hence, the missing side length is 6x - 20