1. The problem asks to write the fraction $-\frac{3}{7}$ as a decimal, using bar notation if necessary. 2. To convert a fraction to a decimal, divide the numerator by the denominator. 3. Divide 3 by 7: $$3 \div 7 = 0.428571428571...$$ 4. The decimal repeats every 6 digits: 428571. This is a repeating decimal. 5. Using bar notation, the decimal representation is: $$-0.\overline{428571}$$ 6. The negative sign is kept as in the original fraction. Final answer: $-0.\overline{428571}$