Answer this -
also can you answer faster kid?

Let's assume the triangle having sides as A, B & C, With an extended exterior side as D. (Refer the above attachement for better view!)

We know that the angles opposite to equal sides of a triangle are equal.

∴ AB = AC ⇒ ∠B = ∠C

Now, Side BA of Triangle ABC has been produced to D.

∴ ∠CAD = ∠B + ∠C (Exterior angle = sum of int. opp. angles)

⇒ 3x - 10 = 25 + x + 15

⇒ 3x - 10 = 40 + x

⇒ 3x - x = 40 + 10

⇒ 2x = 50

⇒ x = 50/2

⇒ x = 25

∴ The value of 'x' in the given figure is 25!