Remember that the sum of the internal angles of every triangle is 180°.
Therefore, find an angle A such that:
[tex]20+40+A=180[/tex]Add 20+40:
[tex]60+A=180[/tex]Substract 60 from both sides to find the value of A:
[tex]\begin{gathered} A=180-60 \\ =120 \end{gathered}[/tex]Therefore, the measure of the remaining angle is 120°.
