1. **State the problem:** Simplify the expression $-\frac{3}{5} + -\frac{3}{4} - \frac{7}{10}$. 2. **Find a common denominator:** The denominators are 5, 4, and 10. The least common denominator (LCD) is 20. 3. **Rewrite each fraction with denominator 20:** $$-\frac{3}{5} = -\frac{3 \times 4}{5 \times 4} = -\frac{12}{20}$$ $$-\frac{3}{4} = -\frac{3 \times 5}{4 \times 5} = -\frac{15}{20}$$ $$-\frac{7}{10} = -\frac{7 \times 2}{10 \times 2} = -\frac{14}{20}$$ 4. **Add the fractions:** $$-\frac{12}{20} + -\frac{15}{20} - \frac{14}{20} = \frac{-12 - 15 - 14}{20} = \frac{-41}{20}$$ 5. **Final answer:** $$-\frac{41}{20}$$ This is an improper fraction and can also be written as a mixed number: $$-2 \frac{1}{20}$$