a)

1 $\frac{1}{4}$ +2 $\frac{5}{6}$ =1 $\frac{6}{24}$ +2 $\frac{26}{24}$ =3 $\frac{26}{24}$ =4 $\frac{2}{24}$ =4 $\frac{1}{12}$

2 $\frac{6}{7}$ + $\frac{5}{6}$  =2 $\frac{36}{42}$ + $\frac{35}{42}$  =2 $\frac{71}{42}$ =3 $\frac{29}{42}$

$\frac{3}{4}$ +1 $\frac{5}{6}$ + $\frac{7}{8}$ = $\frac{18}{24}$ +1 $\frac{20}{24}$ + $\frac{21}{24}$ =1 $\frac{59}{24}$ =3 $\frac{11}{24}$

b)

7 $\frac{3}{5}$ +4 $\frac{5}{7}$ =7 $\frac{21}{35}$ +4 $\frac{25}{25}$ =11 $\frac{46}{35}$ =12 $\frac{11}{35}$  

9 $\frac{7}{8}$ + $\frac{3}{5}$ =9 $\frac{35}{40}$ + $\frac{24}{40}$ =9 $\frac{59}{40}$ =10 $\frac{19}{40}$

3 $\frac{1}{4}$ + $\frac{8}{9}$ +4 $\frac{1}{6}$ =3 $\frac{9}{36}$ + $\frac{32}{36}$ +4 $\frac{6}{36}$ =7 $\frac{47}{36}$ =8 $\frac{11}{36}$

c)

12 $\frac{5}{6}$ +9 $\frac{4}{9}$ =12 $\frac{15}{18}$ +9 $\frac{8}{18}$ =21 $\frac{23}{18}$ =22 $\frac{5}{18}$

6 $\frac{6}{7}$ + $\frac{4}{5}$ =6 $\frac{30}{35}$ + $\frac{28}{35}$ =6 $\frac{58}{35}$ =7 $\frac{23}{35}$

6 $\frac{3}{5}$ +9 $\frac{5}{8}$ +12 $\frac{9}{10}$ =6 $\frac{24}{40}$ +9 $\frac{25}{40}$ +12 $\frac{36}{40}$ =27 $\frac{85}{40}$ =29 $\frac{5}{40}$ =29 $\frac{1}{8}$

d)

25 $\frac{7}{8}$ +17 $\frac{5}{7}$ =25 $\frac{49}{56}$ +17 $\frac{40}{56}$ =42 $\frac{89}{56}$ =43 $\frac{33}{56}$

$\frac{11}{12}$ +1 $\frac{9}{15}$ = $\frac{11}{12}$ +1 $\frac{3}{5}$ = $\frac{55}{60}$ +1 $\frac{36}{60}$  =1 $\frac{91}{60}$  =2 $\frac{31}{60}$

$\frac{1}{3}$ + $\frac{3}{4}$ + $\frac{4}{5}$ +3 $\frac{5}{6}$ = $\frac{20}{60}$ + $\frac{45}{60}$ + $\frac{48}{60}$ +3 $\frac{50}{60}$ =3 $\frac{163}{60}$ =5 $\frac{43}{60}$