The square and the triangle have equal perimeters.
a. find the value of x.
b. find the perimeter.

A) perimeter of square: (x-5) × 4 = 4x-20
perimeter of triangle: 12+ x+ x= 12+ 2x
as the perimeters are equal:
4x -20 = 12+2x
4x -2x = 12+20
(basically, if the numbers "switch sides" the sign, +/- will change)
so,
2x= 32
x= 16

b) perimeter of square is: 4x-20
4x= 16x4= 64
64-20= 44

perimeter of triangle: 12+2x
2x= 32
32+12= 44

hope it helps

That they are numbers and related to each other.