Use the relationship between supplementary angles ∠a and ∠b . What is m∠a if m∠b=121° ?(1 point)
121°
59°
301°
31°
Since ∠a and ∠b are supplementary angles, their measures add up to 180°.
So, if m∠b = 121°, we can substitute this value into the equation:
m∠a + m∠b = 180°
m∠a + 121° = 180°
Subtracting 121° from both sides:
m∠a = 180° - 121°
m∠a = 59°
Therefore, m∠a is 59°. Answer: \boxed{59°}.