\[\boxed{\mathbf{105.}}\]
\[P(A \cap B) = P(B) \cdot P\left( A \middle| B \right).\]
\[\textbf{а)}\ P(A \cap B) = 0,3 \cdot 0,5 = 0,15.\]
\[\textbf{б)}\ P(A \cap B) = \frac{1}{5} \cdot \frac{5}{8} = \frac{1}{8}.\]
\[\textbf{в)}\ P(A \cap B) = 0,72 \cdot 0,25 =\]
\[= 0,72 \cdot \frac{1}{4} = 0,18.\]
\[\textbf{г)}\ P(A \cap B) = 0,34 \cdot 0,2 = 0,068.\]