2/4-3

To solve the expression \( \frac{2}{4} - 3 \):

1. Simplify \( \frac{2}{4} \) which equals \( \frac{1}{2} \) or 0.5.
2. Then, subtract 3 from 0.5:

\[ 0.5 - 3 = -2.5 \]

So, the final answer is \( -2.5 \).