1/8(-8c+16)-1/3(6+3c)

[tex] \frac{1}{8}(-8c+16) - \frac{1}{3}(6+3c) [/tex]

This may look scary, but all you have to do is distribute, first:
[tex](-c+2)-(2+c)[/tex]

Now it's much easier (remember to distribute the negative):
[tex]-c+2-2-c = -2c[/tex]

So, the entire thing simplifies to -2c. NEAT!