In triangle ABC below, the measure of angle A is 20°and the measure of angle B is 3 times larger than the measure of angle C. What is the measure of angle B ?
Given that angle A is \[20°\]
and that angle B is three times larger than angle C,
you can set up the following equation.
\[20°+B+C=180°.\]
Since \[B=3C\],
you have \[20°+3C+C=180°.\]
Combine like terms:
\[20°+4C=180°.\]
Solve for C:
\[4C=160°\];
\[C=40°\].
If \[C=40°\],
then \[B=(40°)(3)=120°\]