Given:
The perimeter of the pentagon, P=56 units.
From the figure, the sides of the pentagon are 2x, 10, x+2, 3x-2 and 10.
The sum of sides of the pentagon is equal to its perimeter.
Hence, the perimeter can be expressed as,

Now, put P=56 in the above equation and solve for x.

Therefore, the value of x is 6.