Answer:
Explanation:
In an isosceles triangle, two sides and two angles are equal. 
The shortest side of an isosceles triangle is 2x+5 inches. The 2 longest sides are 3 inches longer. This means that the length of each of the longer sides is 
2x + 5 + 3 = 2x + 8 inches
The formula for determining the perimeter of a triangle is expressed as 
Perimeter = a + b + c
Where a, b and c are the sides of the triangle.
The perimeter of the triangle is 21 inches. Therefore, the equation that can be used to find the length of each side of the triangle is 
2x + 5 + 2x + 8 + 2x + 8 = 21
6x + 21 = 21