[tex]\displaystyle\bf\\C_{6} ^{4} +C_{6} ^{5} +C_{6} ^{6} =\frac{6!}{4!\cdot(6-4)!}+\frac{6!}{5!\cdot(6-5)!} +\frac{6!}{6!\cdot(6-6)!} =\\\\\\=\frac{4!\cdot 5\cdot 6}{4!\cdot 1\cdot 2} +\frac{5!\cdot 6}{5!\cdot 1!}+1=15+6+1=22[/tex]