Question

A square with sides of x + 2 and an equilateral triangle of sides with length 2x have equal perimeters.
x = ?

Answer 1

equilateral triangle means that each of the triangles three sides is equal, the squares sides are also all equal as pre definition of a square.

a triangle has three sides
a square has four sides

sum of squares sides = 4(x+2)
sum of triangles sides = 3(2x)

their perimiters are equal

4(x+2)=3(2x)

just algebra from there