@markr,
Looks like 6. Here's the solution:
[C(2,2)*C(6,1)*C(37,3) + C(2,2)*C(6,2)*C(37,2)] / C(45,6)
C(2,2)*C(6,1)*C(37,3) is the number of ways to pick both supplementary numbers, 1 winning number, and 3 other numbers.
C(2,2)*C(6,2)*C(37,2) is the number of ways to pick both supplementary numbers, 2 winning numbers, and 2 other numbers.
C(45,6) is the number of ways to pick 6 numbers.