a)

$6,48:0,8\cdot \left(-2,25\right)=64,8:8\cdot \left(-2,25\right)=8,1\cdot \left(-2,25\right)=\underline{-18,225}$

Pomocnicze obliczenia pisemne:

$\begin{array}{r}\stackrel{2}{2},\stackrel{4}{2}5\\ \underline{\cdot 8,1}\\ 225\\ \underline{+1800}\\ 18,225\end{array}$

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b)

$\frac{2}{9}\cdot 8,1-5,1:3\frac{2}{5}=\frac{2}{{\cancel{9}}_1}\cdot \frac{{\cancel{81}}^9}{10}-\frac{51}{10}:\frac{17}{5}=\frac{18}{10}-\frac{{\cancel{51}}^3}{10}\cdot \frac{5}{{\cancel{17}}_1}=\frac{18}{10}-\frac{15}{10}=\frac{3}{10}=\underline{0,3}$

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c)

${\left(1\frac{3}{8}-2,5\right)}^2={\left(1\frac{3}{8}-2\frac{1}{2}\right)}^2={\left(1\frac{3}{8}-2\frac{4}{8}\right)}^2={\left(\frac{11}{8}-\frac{20}{8}\right)}^2={\left(-\frac{9}{8}\right)}^2=\frac{81}{64}=\underline{1\frac{17}{64}}$

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d)

${\left(3\frac{2}{3}-5\right)}^2\cdot {\left(1,5\right)}^3={\left(-1\frac{1}{3}\right)}^2\cdot {\left(\frac{3}{2}\right)}^3={\left(-\frac{4}{3}\right)}^2\cdot \frac{27}{8}=\frac{{\cancel{16}}^2}{{\bcancel{9}}_1}\cdot \frac{{\bcancel{27}}^3}{{\cancel{8}}_1}=\underline{6}$