Answer:
∠ E = 57°
Explanation:
Since DF = EF then the triangle is isosceles with 2 base angles congruent , so
∠ E = ∠ D = 4x + 1
The sum of the 3 angles in the triangle = 180°
Sum the 3 angles and equate to 180
4x + 1 + 4x + 1 + 5x - 4 = 180 , collect like terms
13x - 2 = 180 ( add 2 to both sides )
13x = 182 ( divide both sides by 13 )
x = 14
Then
∠ E = 4x + 1 = 4(14) + 1 = 56 + 1 = 57°