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Sum of angles of a triangle is 180.

So, the triangle containging angles 30 & 40, sums upto 70, the third angle becomes 110.

The angle adjacent to 110 becomes 70.

By, the exterior angle property, 45 + x = 70.

Hence, x = 25.

A is the correct answer choice.
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The Sum of all the angles in a triangle is \(180^o\)

In the left traingle: \(40^o + 30^o + third angle^0 = 180^o \)

=> Third angle = \(180^o - 70^o = 110^o\)

Vertically opposite angles are equal and hence third angle in the right lower triangle becomes \(110^o\)

Sum of all the angles in a triangle is \(180^o\)

=> \(110^o + 45^o + x^o = 180^o\)

=> \(x^0 = 180^o - (110^o + 45^o)\)

=> \(x^0 = 25^o \)

Answer A
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