Answer:
90°
Step-by-step explanation:
step 1
Find the measure of angle b
we know that
(m∠b+90°)=124° ----> by vertical angles
so
m∠b=124°-90°
m∠b=34°
step 2
Find the measure of angle c
(m∠c+124°)=180° ----> by supplementary angles (form a linear pair)
m∠c=180°-124°
m∠c=56°
step 3
Find the measure of angle a
m∠a=m∠c ----> by vertical angles
so
m∠a=56°
step 4
Find the value of m∠ a + m∠b
m∠a=56°
m∠b=34°
m∠ a + m∠b=56°+34°
m∠ a + m∠b=90°
