11. \( \frac{1}{3}+\frac{5}{6}-\frac{7}{12} \) 12. \( \frac{3}{8}-\frac{1}{4}+\frac{5}{16} \) 13. \( \frac{4}{9}+\frac{2}{3}-\frac{5}{18} \) 14. \( \frac{5}{7}-\frac{2}{14}+\frac{3}{28} \) 15. \( \frac{2}{5}+\frac{3}{10}-\frac{1}{20} \) 16. \( \frac{7}{12}-\frac{1}{6}+\frac{5}{24} \) 17. \( \frac{3}{5}+\frac{7}{10}-\frac{9}{20} \) 18. \( \frac{5}{8}-\frac{1}{4}+\frac{3}{16} \) 19. \( \frac{4}{15}+\frac{2}{5}-\frac{7}{30} \) 20. \( \frac{9}{14}-\frac{3}{7}+\frac{5}{28} \)

To tackle the addition and subtraction of fractions, it helps to first find a common denominator, which allows for easy combining of the numerators. For instance, in the first problem, the denominators are 3, 6, and 12; the least common multiple (LCM) is 12. By converting each fraction to have the same denominator, you can combine them seamlessly and simplify the final result! When working with fractions, a common mistake is forgetting to adjust all fractions to the common denominator before combining them. Always double-check your calculations, especially when reducing fractions afterward, as it's easy to misplace a number or overlook simplification steps. An effective strategy is to write the entire equation out step-by-step to minimize errors!