In the diagram above, < CDE = < CED = 15^o

(base < s of isos. \(\bigtriangleup\))

< ECD = 180^o - (15 + 15)^o

= 180^o - 30^o = 150^o

But x + 110^o = 150^o

(Sum of opp. interior < s of a\(\bigtriangleup\) = opp. exterior < )

x = 150^o - 110^o = 40^o