Someone please explain how to get the answers

Answer:
[tex] m\angle A =40\degree [/tex]
[tex] m\angle D =40\degree [/tex]
Step-by-step explanation:
By inscribed angle theorem:
[tex] m\angle A = \frac{1}{2} \times 80\degree [/tex]
[tex] m\angle A =40\degree [/tex]
[tex] m\angle D= \frac{1}{2} \times 80\degree [/tex]
[tex] m\angle D =40\degree [/tex]