If A is a subset and equal to B then B'-A' is equal to​

A-B

Step-by-step explanation:

It doesn't say A=B... But just that A is a subset of B.

Anyways, why not try an example to help reveal the answer.

Let the universe set, U, be U={1,2,3,4,5,6}.

Let B={1,2,3,4} and A={1,3,5}

First choice would become A'={2,4,6}

Second choice would become B'={5,6}

Third choice would become A-B={5}

Fourth choice is just { }

B'-A'={5}

The only choice matching is A-B

*Just so you know X-Y is the set of elements contained in X only if they are not also in Y.

there are lots of ways.   pick's theorem tells us if the vertices are lattice points the area a is

a = b/2 + i - 1

where b is the number of boundary lattice points and i is the number of interior lattice points.

in the figure i count b=16, i=50 so

a = 8 + 50 - 1 = 57

let's try the shoelace formula.   the area is half the sum of the cross products of the sides.  

a(-2,6)   -2(2)-6(-5) = 26

b(-5,2)   -5(-3) - 2(-2) = 19

c(-2,-3) -2(-3) - (-3)(4) = 18

d(4,-3)   4(3) - (-3)(5) = 27

e(5,3)   5(3) - 3(1) = 12

f(1,3)     1(6) - 3(-2) = 12

a(-2,6)

each of the cross products is twice the area of the triangle with the associated side and one vertex the origin. so the area of abo=26/2=13.

area = (1/2) (26 + 19 +   18 + 27 + 12 + 12) = 57

that checks!