Answer:
[tex] \boxed{\angle b = 12 \degree} [/tex]
Given:
[tex]\angle a \: and \: \angle b \: are \: complementary \: angles\\ \\ \angle a = 78 \degree [/tex]
Step-by-step explanation:
Two Angles are Complementary when they add up to 90° (a Right Angle).
[tex] = > \angle a + \angle b = 90 \degree \\ \\ = > 78 \degree + \angle b = 90\degree \\ \\ = > \angle b = 90 \degree - 78 \degree \\ \\ = > \angle b = 12 \degree[/tex]
