Đáp án:
$\begin{array}{l}
1)a)\frac{5}{9}.26\frac{1}{2} - \frac{5}{9}.44\frac{1}{2} = \frac{5}{9}\left( {26\frac{1}{2} - 44\frac{1}{2}} \right)\\
= \frac{5}{9}\left( { - 18\frac{1}{2}} \right) = \frac{5}{9}.\left( { - \frac{{39}}{2}} \right) = \frac{{ - 5.13}}{{3.2}} = \frac{{ - 65}}{6}\\
b)\left( { - 2,5} \right).\left( { - 8,3} \right).\left( { - 4} \right) = \left( {2,5.4} \right).\left( { - 8,3} \right) = 10.\left( { - 8,3} \right) = 83
\end{array}$
$\begin{array}{l}
2)a)\frac{{ - 10}}{{21}}.x = \frac{3}{5}\\
\Rightarrow x = \frac{3}{5}:\frac{{\left( { - 10} \right)}}{{21}}\\
\Rightarrow x = \frac{3}{5}.\frac{{ - 21}}{{10}}\\
\Rightarrow x = \frac{{ - 63}}{{50}}\\
b)\left| {x - 3,7} \right| + 1,9 = 2,3\\
\Rightarrow \left| {x - 3,7} \right| = 2,3 - 1,9 = 0,4\\
\Rightarrow \left[ \begin{array}{l}
x - 3,7 = 0,4\\
x - 3,7 = - 0,4
\end{array} \right.\\
\Rightarrow \left[ \begin{array}{l}
x = 4,1\\
x = 3,3
\end{array} \right.
\end{array}$
