Answer :
All three angles on a triangle always equal 180°.
Example: 100°+40°+40°=180°
102+39=141°
180-141=39°
x = 39°
Example: 100°+40°+40°=180°
102+39=141°
180-141=39°
x = 39°
When you add up all the angles it should equal to 180 so 180-102=78 then 78-39=39 so x=39
