The perimeter of a shape is the sum of the sides. The perimeters of both shapes are equal.
2x+2x-14=x+2+x+9+x-7
Combine like terms
4x-14=3x+4
Subtract 3x from both sides
x-14=4
Add 14 to both sides
x=18
Now substitute x in for each perimeter.
4*18-14=58
The perimeter of the rectangle is equal to 58 units.
3*18+4=58
The perimeter of the triangle is equal to 58 units.