Use the relationship between supplementary angles ∠a and ∠b. What is m∠a if m∠b=121°?(1 point)

A. 31°

B. 121°

C. 301°

D. 59°

1 answer

Supplementary angles are two angles whose measures add up to 180 degrees. Given that \( m∠b = 121° \), we can determine \( m∠a \) using the equation:

\[ m∠a + m∠b = 180° \]

Substituting the value of \( m∠b \):

\[ m∠a + 121° = 180° \]

Now, subtract 121° from both sides to solve for \( m∠a \):

\[ m∠a = 180° - 121° = 59° \]

Therefore, \( m∠a = 59° \). The correct answer is:

D. 59°