[tex]C^2_4 \to \frac{4!}{2!(4-2)!}=\frac{\not 1* \not 2*3*4}{\not 1* \not 2*2!}=\frac{3* \not 4}{1* \not 2}=3*2 \to 6 \\\\\\ C^1_6 \to \frac{6!}{1!(6-1)!}=\frac{\not 1*2*3..*6}{\not 1 * 5!}=\frac{\not 2* \not 3* \not 4 * \not 5 *6}{1* \not 2* \not 3* \not 4 * \not 5}\to 6[/tex]
[tex]A^2_4 \to \frac{4!}{(4-2)!}=\frac{1*2*3*4}{2!}=\frac{\not 1* \not 2*3*4}{\not 1*\not 2}=3*4 \to12 \\\\\\P_3=3! =1*2*3 \to 6[/tex]
[tex]C^2_4-C^1_6+A^2_4-P_3=6-6+12-6= \\\\=12-6=\\\\=\boxed{6} [/tex]
