\[\boxed{\mathbf{40}\mathbf{.}}\]
\[\textbf{а)}\ 1,\ 2,\ 3:\]
\[12,\ 13,\ 11,\ 21,\ 23,\ 22,\ 31,\ 32,\ 33.\]
\[\textbf{б)}\ 4,\ 5,\ 6:\]
\[45,\ 46,\ 44,\ 54,\ 55,\ 56,\ 64,\ 65,\ 66.\]
\[\textbf{в)}\ 7,\ 8,\ 9:\]
\[78,\ 79,\ 77,\ 87,\ 88,\ 89,\ 97,\ 98,\ 99.\]