\( \begin{array}{ll}\text { 13. } 4 \frac{9}{100}+5 \frac{11}{100} & \text { 14. } 4 \frac{9}{100}-5 \frac{11}{100} \\ \text { 6. } 2 \frac{1}{2}-\frac{2}{5} & \text { 17. } 3 \frac{1}{4}+1 \frac{1}{2} \\ \text { 9. } 2 \frac{1}{3}+1 \frac{1}{2} & \text { 20. } 2 \frac{1}{3}-1 \frac{1}{2}\end{array} \)

Let’s tackle the additions and subtractions involved here like math superheroes! For \(4 \frac{9}{100}+5 \frac{11}{100}\), first convert these mixed numbers to improper fractions. You get \(\frac{409}{100} + \frac{511}{100} = \frac{920}{100} = 9.2\). For the subtraction \(4 \frac{9}{100}-5 \frac{11}{100}\), similarly, \(\frac{409}{100} - \frac{511}{100} = \frac{-102}{100} = -1.02\). Now, for \(2 \frac{1}{2}-\frac{2}{5}\), convert to a common denominator of 10: \(\frac{25}{10} - \frac{4}{10} = \frac{21}{10} = 2.1\). For \(3 \frac{1}{4}+1 \frac{1}{2}\), convert to improper fractions: \(\frac{13}{4} + \frac{3}{2} = \frac{13}{4} + \frac{6}{4} = \frac{19}{4} = 4.75\). Go forth and conquer those numbers! It’s all about playing with fractions like a math magician.