Can someone solve this problem for me???

[aeager1]

It is in the official gmat review 12th edition pg.144
I have the answer but I want to see it worked out!

(20-n)+n+(18-n)=25

[cans]

(20-n)+n+(18-n)=25
well you can write it as:- 20-n+n+18-n=25
20+18-n=25
38-n=25
38-25=n
or n=13

[Tani]

The formula is

G1 + G2 - B + N = T

(The total in group one), plus (the total in group two) minus (those items in both groups one and group two - i.e.those items that would have been double-counted) plus (those items not included in any group) equals the total.

With this problem you get 20 + 18 - n + 0 = 25 Therefore n = 13.