Answer: a is the # of elements in A but NOT B, that is A ONLY
b is the # of elements in B but NOT A, that is B only
N is the # of elements in the INTERSECTION of A and B
a + N = 99
b + N = 25
a + b + N = 123
Subtracting the first two equations: a - b = 74
Subtracting the last two equations: -a = -98
a = 98
So then a - b = 74 and a = 98
98 - b = 74
-b = -24
b = 24
a = 98, b = 24 and a + b + N = 123
98 + 24 + N = 123
122 + N = 123
N = 1
98 are in A only
24 are in B only , which is the answer to the question
1 is in both A and B
Step-by-step explanation:
