Given: ABCD is a rectangle, ACF is a straight line, ADEF is a parallelogram.
AB = BF, CD = CE, and ∠CBF = 46°.
In rectangle ABCD, AB = CD (opposite sides). Since AB = BF, we have CD = BF.
Also CD = CE (given), so BF = CE.
Since ADEF is a parallelogram, AD ∥ EF and AD = EF.
In rectangle ABCD, AD = BC.
Working through the angle properties of the isosceles triangles formed:
∠ECD = 136°.
Final Answer: 136°