There are
ways of building a subset of
elements from
, so the total number of subsets you can build is

Recalling the binomial theorem, the above sum is equal to

as required.
Answer:
C. 21/26
Step-by-step explanation:
Slope Formula: 
Plug in our coordinates:
m = (5 + 16)/(18 + 8)
m = 21/26
3x + 3 = 3y < -- make this 3x - 3y = -3
2x - 6y = 2
multiply by 2 on the first equation
6x - 6y = -6
2x - 6y = 2
subtract them
4x = -8
x = -2
substitute x = -2 into any of the equation
2x - 6y = 2
2(-2) - 6y = 2
-4 - 6y = 2
-6y = 6
y = -1
So the answer is
(-2 , -1)