An obtuse triangle has one obtuse angle, or an angle that measures more than 90° but less than 180°. Options 1 and 2 are not correct, because these are acute angles.
So, one of the angles must be 40°, and the other may be 100° or 120°.
The measures of the angles in a triangle add up to 180°.
\(40^\circ + 40^\circ +x = 180^\circ \\
80^\circ + x=180^\circ \\
x=180^\circ - 80^\circ \\
x=100^\circ\)
The other two angles are 40° and 100°.
