AC= 24, DC=12
1) Considering that these line segments AC measures twice the size of AD, and AD+DC=AC
AC= 2*AD
AC=2*12
2) Plugging in
AC=2* 12
4y-36=AC
4y-36=24
4y-36+36=24+36
4y=60
y=15
So, AC = 4(15) -36 Then AC =60-36=24
Since DC measures the same as AD, then DC= 12
AC= 24, DC=12