the problem is as follows:

Partners in an accounting firm.

Assume that each partner has at least one specialization.

Specialization-------------Number

Auditing---------------------13

Consulting------------------14

Tax--------------------------11

Auditing and consulting-----8

Auditing and tax-------------6

Consulting and tax----------7

All three---------------------3

How many partners are there?

i know that the problem would be set up like the picture I drew below, and that i'm trying to find ((A ∪ C) ∪ T), but i just can't figure it out.