<h3>
Answer: 
</h3>
Explanation:
The identity we'll use is cos(-x) = cos(x) for any value of x.
So cos(-150) = cos(150).
Then locate the angle 150 on the unit circle. The terminal point is 
The x coordinate of this terminal point is the value of cos(150).
Let 
be the number of days spent at Tahoe and San Francisco, respectively.
We don't know the values of 
and 
yet, but we know that the holiday lasted 9 days:
We also know that each day spent in Tahoe costed 350 and each day spent in San Francisco costed 475. So, the total cost of the holiday is the sum of the number of days muliplied by their cost:
If we put the two equations together, we have the system
Which yields
Answer:
The answer is obviously letter A!
