Question

If the exterior ∠ACD of ΔABC has the measure 120 and one of two internal opposite angles has the measure 40, then find the measures of the remaining angles of ΔABC.

Answer 1

Let angles of triangle be A, B, C
We know that by exterior angle property
angle ACD=B+C
Given that, B=40
Then by property
120=40+C
C=80
By angle sum property
A+B+C=180
A+40+80=180
A+120=180
A=180-120
A=60
I hope this is helpful