The sum of all interior angles in a triangle is 180°.
m∠q + m∠r + m∠s = 180°
1x + 3x + 6x = 180
10x = 180
x = 180/10
x = 18
m∠q = (1x)° = 1 x 18 = 18°
m∠ r = (3x)° = 3 x 18 = 54°
m∠s = (6x)° = 6 x 18 = 108°
m∠s is the obtuse angle because its measure is more than 90°. Its angle measures 108°