Question

find the lettered angle

Answer 1

in ∆ACD,
AC=CD so D = 2x.
Now exterior angle property
angle ACB = 2x+D = 4x

In ∆ABC,AB=AC
So B=C = 4x
now angle sum property
ANGLE A+B+C =180^
x+4x+4x=180°
9x=180°
so x= 20°

Answer 2

Answer:

in ∆ACD,

AC=CD so D = 2x.

Now exterior angle property

angle ACB = 2x+D = 4x

In ∆ABC,AB=AC

So B=C = 4x

now angle sum property

ANGLE A+B+C =180^

x+4x+4x=180°

9x=180°

so x= 20°