\[
\begin{align*}
a) & \quad \frac{3}{-3} + \frac{2}{-21} + \frac{-3}{9} + \frac{-2}{-3} + \frac{1}{-3} + \frac{1}{3} + \frac{-2}{21} + \frac{1}{21} + \frac{21}{21} + \frac{21}{21} \\
b) & \quad \frac{-2}{3} + \frac{-6}{5} + \frac{-10}{15} + \frac{-18}{15} + \frac{-8}{15} \\
c) & \quad \frac{13}{-15} + \frac{-5}{78} \\
d) & \quad \frac{-3}{-3} + \left( -\frac{5}{6} \right) \\
e) & \quad \frac{1}{-12} + \frac{1}{78} \\
f) & \quad \frac{-9}{-7} - \frac{2}{-13} \\
g) & \quad \frac{-18}{75} + 0.3 \\
h) & \quad 3.5 - \left( \frac{-2}{9} \right) \\
i) & \quad -2.5 \cdot \left( \frac{-3}{25} \right) \\
k) & \quad \frac{2}{3} - \frac{-7}{9} \\
l) & \quad \frac{-6}{13} \cdot \frac{9}{-26} \\
m) & \quad \left( -\frac{15}{7} \right) : \left( -\frac{23}{14} \right) \\
n) & \quad \left( -6, 5 \right), \left( -\frac{7}{27} \right) \\
\end{align*}
\]
c: \(\frac{13}{-15}+\frac{-5}{18}=\frac{-13}{15}-\frac{5}{18}=-\frac{78}{90}-\frac{25}{90}=\frac{-78-25}{90}=-\frac{103}{90}\)
d: \(\left(-3\right)-\left(-\frac56\right)=-3+\frac56=-\frac{18}{6}+\frac56=-\frac{13}{6}\)
e: \(\frac{-1}{12}+\frac{-1}{18}=-\frac{3}{36}+\frac{-2}{36}=-\frac{5}{36}\)
f: \(-\frac34-\frac92=-\frac34-\frac{18}{4}=-\frac{21}{4}\)
g: \(-\frac{18}{15}+0,3=-\frac65+\frac{3}{10}=-\frac{12}{10}+\frac{3}{10}=-\frac{9}{10}\)
h:\(3,5-\left(-\frac27\right)=\frac72+\frac27=\frac{49}{14}+\frac{4}{14}=\frac{53}{14}\)
i: \(-2,5\cdot\frac{-3}{25}=2.5\cdot\frac{3}{25}=\frac{7.5}{25}=\frac{3}{10}\)
k: \(2\frac34\cdot\frac{-4}{9}=\frac{11}{4}\cdot\frac{-4}{9}=-\frac{11}{9}\)
l: \(-\frac{6}{13}:\frac{9}{-26}=\frac{6}{13}\cdot\frac{26}{9}=\frac69\cdot\frac{26}{13}=\frac23\cdot2=\frac43\)
m: \(\left(-1\frac57\right):\left(-2\frac{3}{14}\right)=-\frac{12}{7}:\frac{-31}{14}=\frac{12}{7}\cdot\frac{14}{31}=\frac{12\cdot2}{31}=\frac{24}{31}\)
m: \(\left(-6,5\right)\cdot\frac{-7}{27}=\frac{13}{2}\cdot\frac{7}{27}=\frac{91}{54}\)
\(c)\frac{13}{-15}+\frac{-5}{18}=\frac{-78}{90}+\frac{-25}{90}=-\frac{103}{90}\)
\(d.\left(-3\right)-\left(-\frac56\right)=-\frac{18}{6}+\frac56=-\frac{13}{6}\)
\(f.\frac{-3}{4}-\frac92=-\frac34-\frac{18}{4}=-\frac{21}{4}\)
\(g.\frac{-18}{15}+0,3=-\frac{36}{30}+\frac{9}{30}=-\frac{27}{30}=-\frac{9}{10}\)
\(h.3,5-\left(-\frac27\right)=\frac{49}{14}+\frac{4}{14}=\frac{53}{14}\)
\(i.-2,5\cdot\left(-\frac{3}{25}\right)=-\frac52\cdot\left(-\frac{3}{25}\right)=\frac{3}{10}\)
\(k.2\frac34\cdot\frac{-4}{9}=\frac{11}{4}\cdot\frac{-4}{9}=-\frac{11}{9}\)
\(l.\frac{-6}{13}:\frac{9}{-26}=-\frac{6}{13}\cdot\frac{-26}{9}=\frac43\)
\(m.\left(-1\frac57\right):\left(-2\frac{3}{14}\right)=-\frac{12}{7}\cdot\frac{-14}{31}=\frac{24}{31}\)
\(n.\left(-6,5\right)\cdot\left(-\frac{7}{27}\right)=\left(-\frac{13}{2}\right)\cdot\left(-\frac{7}{27}\right)=\frac{91}{54}\)
