Answer:
x = 15
Step-by-step explanation:
angles 2 and 4 are supplementary so they add up to 180
2x + 10 + 4x + 80 = 180
6x + 90 = 180
6x = 90
x = 15
The perimeter of each is the sum of the lengths of its sides.
Triangle Perimeter = 16 + 4x-3 +3x = 7x+13
Square Perimeter = 2x +2x +2x +2x = 8x
If these are equal, you have

The length of a side of the square is 26 units.