\[\boxed{\mathbf{125.}}\]
\[СС = \frac{1}{3};\]
\[СК = \frac{1}{3};\]
\[КС = \frac{1}{3}.\]
\[\textbf{а)}\ Р(СС) = \frac{1}{3}.\]
\[\textbf{б)}\ Р(СК\backslash КС) = \frac{1}{3} + \frac{1}{3} = \frac{2}{3}.\]