Answer
Option 1 is correct.
The triangle is an isosceles triangle.
Step-by-step explanation
Noting that the sum of angles in a triangle is 180°.
We can solve for each of the angles in this triangle to obtain the type of triangle it is.
The angles of the triangle are 2x, (3x - 15) and (7x + 15)
2x + 3x - 15 + 7x + 15 = 180°
2x + 3x + 7x - 15 + 15 = 180°
12x = 180°
Divide both sides by 12
(12x/12) = (180°/12)
x = 15°
We can then solve for the measures of the three angles now
2x = 2 (15°) = 30°
3x - 15 = 3 (15°) - 15° = 45° - 15° = 30°
7x + 15 = 7 (15°) + 15° = 105° + 15° = 120°
So, the angles of the triangle are 30°, 30° and 120°
A tringle that has two of its angles equal to each other is called an isosceles triangle.
Hope this Helps!!!