Answer:
DE = 8
Step-by-step explanation:
Since the 3 angles are congruent then the triangle is equilateral with 3 congruent sides , then
5x - 12 = 3x - 4 ( subtract 3x from both sides )
2x - 12 = - 4 ( add 12 to both sides )
2x = 8 ( divide both sides by 2 )
x = 4
Then
EF = 3x - 4 = 3(4) - 4 = 12 - 4 = 8 , so
DE = EF = 8
