Find y, if x = 60.
a) 30°
b) 35°
c) 40°
d) 45°

In triangle ADC and BCD, AD = BC (opposite sides of a rectangle are congruent)

Step-by-step explanation:

As congruent means shapes having the same length and same internal angles.  In the given figure the two statements are already written. The only information about sides AD and BC are missing to complete the proof of congruent diagonals.