Answer: x=5
Explanation:
isosceles triangles consist of a base side and two congruent legs
if the length of the base is x and the leg is 2x-2, the other leg must also be 2x-2
the lengths of the sides of the triangle are x, 2x-2, 2x-2
the perimeter, the total length of the sides, is 21
x+2x-2+2x-2=21
5x-4=21
5x=25
x=5