Sprowadzamy liczby do ułamków zwykłych albo dziesiętnych tak, aby wygodnie wykonać działania.

a)

$1,245+\frac{3}{4}=1,245+0,75=1,995$

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b)

$1,2+\frac{5}{6}=\frac{6}{5}+\frac{5}{6}=\frac{36}{30}+\frac{25}{30}=\frac{61}{30}=2\frac{1}{30}$

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c)

$4,35-\frac{3}{200}=\frac{870}{200}-\frac{3}{200}=\frac{867}{200}=4,335$

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d)

$4,8-1\frac{1}{3}=\frac{24}{5}-\frac{4}{3}=\frac{72}{15}-\frac{20}{15}=\frac{52}{15}=3\frac{7}{15}$

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e)

$5,4-\frac{5}{4}=\frac{27}{5}-\frac{5}{4}=\frac{108}{20}-\frac{25}{20}=\frac{83}{20}=4,15$

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f)

$\frac{7}{8}-0,78=\frac{175}{200}-\frac{156}{200}=\frac{19}{200}=0,095$

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g)

$1\frac{2}{5}-0,85+3\frac{7}{20}=\frac{28}{20}-\frac{17}{20}+\frac{67}{20}=\frac{78}{20}=\frac{39}{10}=3,9$

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h)

 $33,3+\frac{1}{3}-1,25=\frac{333}{10}+\frac{1}{3}-\frac{5}{4}=\frac{1998}{60}+\frac{20}{60}-\frac{75}{60}=\frac{1943}{60}=32\frac{23}{60}$

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i)

$3\frac{3}{25}-(0,8-\frac{1}{4})=\frac{78}{25}-(\frac{4}{5}-\frac{1}{4})=\frac{78}{25}-\frac{11}{20}=\frac{312}{100}-\frac{55}{100}=\frac{257}{100}=2,57$

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j)

$3,25-1\frac{1}{3}-1,5=\frac{13}{4}-\frac{4}{3}-\frac{3}{2}=\frac{39}{12}-\frac{16}{12}-\frac{18}{12}=\frac{5}{12}$