Answer:
#2 = 70
#3 = 40
using the Angle sum property and opposite angle
Answer:
The correct answer is not shown in your picture. You must get a = 60.
Step-by-step explanation:
(1/2)a + (2/3)b = 50
b = 30
(1/2)a + (2/3)(30) = 50
(1/2)a + 20 = 50
(1/2)a + 20 - 20 = 50 - 20
(1/2)a = 30
2 * (1/2)a = 2 * 30
a = 60
The correct answer is not shown in your picture. You must get a = 60.
Given :

We know the identity
We use this property to simplify the left hand side
So 

we know ,
when
then

For 

Add
on both sides

Finally we add 2npi for general solution
So options C and D are correct
It hard for me too but I think I got it