answer:
d: 30
all angles in a triangle have a sum of 180 degrees. Just add 50 and 100 (so 150) and do 180-150=30.
The angle on one side of a straight line is 180°, so 40° + 60° + h = 180°.
If you rearrange this you will get h = 180° - 60° - 40°, this will give you: h = 80°.
Hope this helps
