Question

n(A)=285, n(B)=195, n(U)=500, n(AUB)=410 , find n(A'UB')

Answer 1

the answer is...
215+305= 520

Answer 2

n(AUB) = n(A) + n(B) - n(A n B)
410 = 285 + 195 - n(AnB)
n(AnB)  = 285 + 195 - 410
             =  70

n(AnB)' = U - n(AnB)
            = 500 -  70  = 430
By Demorga's Theorem
  n(A' U B') = n(A n B)'
                 =  430