OG12 ds #140

[papgust]

In the figure above [Please refer OG 12], what is the value of x + y ?
(1) x = 70
(2) ABC and ADC are both isosceles triangles.

OA: E

Tried to search for the question and couldn't find any. Hope that the question is not discussed.

Can someone explain?

[kstv]

Searched in Google Book I saw the solution at Page 337 Oops !
Keeping that aside.
ABC and ADC are two isosceles traingle having the same base AC - Condition (2).
It does not mention in what ration side DA divides the angel CAB.
Suppose I flip the triangle ADC along AC.
ABCD will be a quadrilateral.
AB = BC and AD = DC.
angle BAC = BCA = 55° if x is 70 Condition (1)
but nothing can be deduced about = angles DAC or DCA only that they are less then 55°
and y > 70°
so E.