Answer:
y = 15
Step-by-step explanation:
Consider that the attached screenshot is the figure given in the problem. Also consider that DC = 12, due to the fact that AD = 12, and there is a midpoint at point D.
AD + DC = AC
12 + 12 = 4y - 36
24 = 4y - 36
+ 36 + 36
60 = 4y
60/4 = 4y/4
y = 15
