00:01
Okay, when you see the n, the n is asking you for criminality, which simply is how many elements are in the set.
00:28
So a has 1, 2, 3, 4, 5, 6, 7, 8, 9.
00:35
1, 2, 3, 4, 6, 7, 8, 9.
00:38
So it has 9 numbers in it.
00:42
Not a.
00:44
Well, if there are 9 numbers, in so from 1 to 20 so 20 minus 9 is 11 so there would be 11 because not a would be not a equals 1 3 4 5 7 10 11 12 we've got 13 14 15 15 16 17 17 17 17 so 1 2 3 3 14 17 17 so 1 2 3 4 five, six, seven, eight, nine, ten, eleven.
01:27
B, how many are in b? one, two, three, four, five, six, seven, eight.
01:35
A, intersect b...