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
(-3, 3) because it is the intersection point.
Since the lines a and b are parallel, <4 and <8 are of the same measure. To find <8, we can simply subtract the measure of <7 from 180 degrees.
<4 = <8 = 180 - <7 = 180- 114 = 66 degrees
You have to choose
members from the group of
people. So there are
ways to do it.
