Question

(angle3) is a supplement of (angle4), and (mangle3 = 57^{circ}). find (mangle4).
a (57^{circ})
b (114^{circ})
c (33^{circ})
d (123^{circ})

Explanation:

Step1: Recall supplement - angle relationship

Supplementary angles add up to 180°. So, $m\angle3 + m\angle4=180^{\circ}$.

Step2: Substitute the value of $m\angle3$

Given $m\angle3 = 57^{\circ}$, we have $57^{\circ}+m\angle4 = 180^{\circ}$.

Step3: Solve for $m\angle4$

$m\angle4=180^{\circ}- 57^{\circ}=123^{\circ}$.

Answer:

D. 123°