3/10 ÷ (-9/20)

1. Rewrite division as multiplication by the reciprocal: $$\frac{3}{10} \times (-\frac{20}{9})$$

2. Multiply the fractions: $$- \frac{3 \times 20}{10 \times 9}$$

3. Simplify: $$- \frac{60}{90} = -\frac{2}{3}$$