Your answer will 21,22,23,24,25,26,
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
Answer: D
Step-by-step explanation:
because 320/4 = 80 mi/hr because it can not km or min and hr^2 would not make any sense
So we know we don't want to exceed 18 dollars.
So what we want to know is how many times can 2 dollars go into 18 dollars.
We would do

Now the answer is 9, so we know we can buy 9 pounds of apples without going over 18 dollars.