For the first triangle x=70. 180-40 is 140. Divided that by 2 and you’d get 70.
The second triangle x=90. 180-45 is 135. 135-45 (the angle congruent to the other 45 degree angle) is 90.
The third triangle x=65. 180-50 is 130. 130 divided by two is 65.
Check all answers by adding all the angles of the triangle and make sure they equal 180
