To divide by a fraction, you can multiply by its reciprocal.
So, when you divide 3 by three-fifths, you can rewrite it as:
\[ 3 \div \frac{3}{5} = 3 \times \frac{5}{3} \]
Now, you can simplify this:
\[ 3 \times \frac{5}{3} = \frac{3 \times 5}{3} = \frac{15}{3} = 5 \]
Thus, the result of \( 3 \div \frac{3}{5} \) is \( 5 \).
So the answer is 5.