Answer:
B
Explanation:
Since ∠ E = ∠ F then the triangle is isosceles and DF = DE, that is
6x = x + 2y ( subtract x from both sides )
5x = 2y ( subtract 2y from both sides )
5x - 2y = 0 → (1)
and perimeter = 29, that is
6x x + 2y + 5x - y = 29 , simplifying
12x + y = 29 → (2)
Multiply (2) by 2
24x + 2y = 58 → (3)
Add (1) and (3) term by term to eliminate y, that is
29x = 58 ( divide both sides by 29 )
x = 2
Substitute x = 2 into (2) and evaluate for y
12(2) + y = 29
24 + y = 29 ( subtract 24 from both sides )
y = 5
Thus
FE = 5x - y = 5(2) - 5 = 10 - 5 = 5 → B