Question

How do I figure this out

Answer 1

• x = 21

Explanation:

Given triangle is equilateral since all three angles marked as congruent.

It means each interior angle measures 60°.

The angle (5x + 15)° is exterior angle.

We know exterior angle measure is same as the sum of non-adjacent interior angles:

• 5x + 15 = 60 + 60
• 5x + 15 = 120
• 5x = 120 - 15
• 5x = 105
• x = 105/5
• x = 21