To get the type of triangle mentioned we need to find the value of x first. Sum of angles in a triangle add up to 180°, thus 2x+(3x-15)+(7x+15)=180 2x+3x-15+7x+15=180 12x=180 x=15° thus the respective sizes will be: 2x=30° 3x-15=30° 7x+15=120° Since the triangle has two congruent angles we conclude that the triangle is called Isosceles triangle
