math hw
posted by David on .
In set of 30 different positive integers, every number is even and/or a multiple of 3. If 22 of these numbers are even and 15 are multiple of 3, then how many of these numbers are multiple of 6?

all multiples of 6 are even and multiples of 3
Venn diagram (intersection is mult of 6)
n are multiples of 6
22  n are even only
15  n are 3 only
(22 n) + n + (15n) = 30
37  n = 30
n = 7