Đáp án:
$a)\dfrac{965}{32}\\
b)
x=-3\\
c)x=-2\\$
Giải thích các bước giải:
$a)49\dfrac{8}{23}-\left ( 5\dfrac{7}{32}+14\dfrac{8}{23} \right )+\dfrac{375}{1000}\\
=49\dfrac{8}{23}-5\dfrac{7}{32}-14\dfrac{8}{23} +\dfrac{3}{8}\\
=(49-14)+\left ( \dfrac{8}{23}-\dfrac{8}{23} \right )-\dfrac{167}{32}+\dfrac{3}{8}\\
=35-\dfrac{167}{32}+\dfrac{3.4}{32}\\
=\dfrac{35.32}{32}-\dfrac{155}{32}\\
=\dfrac{965}{32}\\
b)
\dfrac{3}{2}x-\dfrac{2}{3}x=\dfrac{-5}{2}\\
\Leftrightarrow \left ( \dfrac{3}{2}-\dfrac{2}{3} \right )x=\dfrac{-5}{2}\\
\Leftrightarrow \left ( \dfrac{9}{6}-\dfrac{4}{6} \right )x=\dfrac{-5}{2}\\
\Leftrightarrow \dfrac{5}{6}x=\dfrac{-5}{2}\\
\Leftrightarrow x=\dfrac{-5}{2}.\dfrac{6}{5}\\
\Leftrightarrow x=-3\\
c) \dfrac{15}{4}:\left ( 3+\dfrac{1}{4}x \right )=\dfrac{3}{2}\\
\Leftrightarrow \dfrac{15}{4}:\left ( \dfrac{12}{4}+\dfrac{1}{4}x \right )=\dfrac{3}{2}\\
\Leftrightarrow \dfrac{15}{4}:\dfrac{12+x}{4}=\dfrac{3}{2}\\
\Leftrightarrow \dfrac{15}{4}.\dfrac{4}{12+x}=\dfrac{3}{2}\\
\Leftrightarrow \dfrac{4}{12+x}=\dfrac{3}{2}.\dfrac{4}{15}=\dfrac{2}{5}\\
\Leftrightarrow 12+x=\dfrac{4.5}{2}=10\\
\Leftrightarrow x=10-12=-2\\$
