Answer: There are 85 Helena's client own stocks, bonds and mutual funds.
Explanation:
Since we have given that
Let A: who own stocks
B : who own bonds
C : who own mutual fund
So, According to question,
n(A) = 288
n(B) = 200
n(C) = 184
n(A∩B) = 123
n(B∩C) = 106
n( A∩C) = 102
n(A∪B∪C) = 426
As we know the formula :

Hence, there are 85 Helena's client own stocks, bonds and mutual funds.