To simplify the expressions given, we need to handle the operations individually.

1. **Simplifying (-3/25) : 6**:
The division can be rewritten as a fraction. Thus:
\[
\frac{-3/25}{6} = \frac{-3}{25 \cdot 6} = \frac{-3}{150} = \frac{-1}{50}
\]

2. **Simplifying (-5/23) : -2**:
Similarly, we rewrite this division:
\[
\frac{-5/23}{-2} = \frac{-5}{23 \cdot -2} = \frac{-5}{-46} = \frac{5}{46}
\]

Now, we have the results of both operations:

- The result of (-3/25) : 6 is \(\frac{-1}{50}\).
- The result of (-5/23) : -2 is \(\frac{5}{46}\).

Thus, the simplified expressions are:

\[
(-3/25) : 6 = \frac{-1}{50}
\]
\[
(-5/23) : -2 = \frac{5}{46}
\]

If you have further instructions or questions regarding these expressions, feel free to ask!