5)
Equilateral triangle, all sides are equal
So 2x + 5 = 11
2x = 6
x = 3
Answer is the first one
3; Equilateral theorem
6)
Isosceles triangle has at least two congruent sides.
So 6x = 24
x = 4
Answer x = 4
Converse of the Base Angle Theorem
7)
5x + 7 = 52
5x = 45
x = 9
Answer
x = 9
Base angle theorem
8)
5y - 14 = 3y
2y = 14
y = 7
Answer
7; Equiangular theorem