Question

what is the value of u?

u = \boxed{\circ}

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Explanation:

Step1: Use exterior angle theorem

The exterior angle of a triangle equals the sum of the two non-adjacent interior angles, so:
$u + 49^\circ = (3u - 8^\circ) + (u + 18^\circ)$

Step2: Simplify right-hand side

Combine like terms on the right:
$u + 49 = 3u - 8 + u + 18$
$u + 49 = 4u + 10$

Step3: Isolate variable u

Subtract $u$ and 10 from both sides:
$49 - 10 = 4u - u$
$39 = 3u$

Step4: Solve for u

Divide both sides by 3:
$u = \frac{39}{3}$

Answer:

$13$