What is x in this figure?
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Given: The 2 exterior angles of a triangle are 125^o.

To find: We have to find the value of the other exterior angle x.

Solution: 

Now,

∠1 + 125^o = 180^o       (Linear pair of angles)

∠1 = 180^o - 125^o = 55^o     .....(i)

∠2 + 125^o = 180^o       (Linear pair of angles)

∠2 = 180^o - 125^o = 55^o     .....(ii)

∠3 + x^o = 180^o       (Linear pair of angles)

∠3 = 180^o - x^o     .....(iii)

and,

∠1 + ∠2 + ∠3 = 180^o       (Sum of interior angles of a triangle)

Sustitute values from eq. (i), (ii) and (iii):

55^o + 55^o + 180^o - x^o = 180^o

x^o = 55^o + 55^o + 180^o - 180^o      

x^o = 110^o