In both problems, the sum of side lengths is the perimeter. Opposite sides of a parallelogram (or rectangle) are equal in length, so you can find the perimeter by doubling the sum of adjacent sides.
25. 2(x +(x +15)) = (x +45) +(x +40) +(x +25)
.. 4x +30 = 3x +110 . . . . . . . . . . . . . . . . . . . . . . simplify
.. x = 80 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . subtract 3x+30
.. 4x +30 = 4*80 +30 = 240
The perimeter of each is 240 units.
26. 2(x +(x +2)) = (x) +(x +6) +(x +4)
.. 4x +4 = 3x +10 . . . . . . . . . . . . . . . . . . . . . . simplify
.. x = 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . subtract 3x+4
.. 4x +4 = 4*6 +4 = 28
The perimeter of each is 28 units.