Add rational numbers: fractions with unlike denominators

Give the answer as a fraction in lowest terms, or a whole number.

1. Evaluate: 1/10 + (−7/10) (Write a fraction in lowest terms, or a whole number.)
2. Evaluate: 1/2 + (−1/6) (Write a fraction in lowest terms, or a whole number.)
3. Evaluate: −1/2 + (−1/8) (Write a fraction in lowest terms, or a whole number.)
4. Evaluate: 1/4 + (−1/3) (Write a fraction in lowest terms, or a whole number.)
5. Evaluate: 1/5 + (−1/2) (Write a fraction in lowest terms, or a whole number.)
6. Evaluate: 1/2 + 1/2 (Write a fraction in lowest terms, or a whole number.)
7. Evaluate: 3/8 + 1/2 (Write a fraction in lowest terms, or a whole number.)
8. Evaluate: 4/5 + 3/5 (Write a fraction in lowest terms, or a whole number.)
9. Evaluate: −4/7 + 3/8 (Write a fraction in lowest terms, or a whole number.)
10. Evaluate: −1/2 + 3/8 (Write a fraction in lowest terms, or a whole number.)
11. Evaluate: −4/7 + 8/9 (Write a fraction in lowest terms, or a whole number.)
12. Evaluate: 1/4 + (−1/2) (Write a fraction in lowest terms, or a whole number.)
13. Evaluate: −5/8 + 1/3 (Write a fraction in lowest terms, or a whole number.)
14. Evaluate: −4/5 + 3/4 (Write a fraction in lowest terms, or a whole number.)
15. Evaluate: 3/7 + (−1/9) (Write a fraction in lowest terms, or a whole number.)
16. Evaluate: −7/8 + (−9/10) (Write a fraction in lowest terms, or a whole number.)
17. Evaluate: −6/7 + 2/3 (Write a fraction in lowest terms, or a whole number.)
18. Evaluate: −2/3 + 5/6 (Write a fraction in lowest terms, or a whole number.)
19. Evaluate: −13/15 + (−2/3) (Write a fraction in lowest terms, or a whole number.)
20. Evaluate: −1/2 + (−1/2) (Write a fraction in lowest terms, or a whole number.)