Explanation:
your a. is wrong.
so, we need to do both.
a.
you did not really read carefully. DE = 4x and not 4.
DE = 4x does not mean x = 4. absolutely not.
so, you cannot just use x=4 in the first triangle.
but you are right, AB and DE correlate between the 2 congruent triangles.
therefore
3x + 6 = 4x
6 = x
so, AB = 3x + 6 = 3×6 + 6 = 18 + 6 = 24 ft
b.
congruent means that the sides and the angles are the same between the 2 triangles.
so,
6y + 12 = 8y + 2
12 = 2y + 2
10 = 2y
y = 5
so, the angle EDF is
8y + 2 = 8×5 + 2 = 40 + 2 = 42°