Đáp án:
1)
a) $0$
b) $\dfrac{-31}{20}$
2)
$a) x=\dfrac{-1}{10}\\
b)
x=\dfrac{6}{7}$
Giải thích các bước giải:
1)
a) 0,5+0,5.(-80).0,01-10%
$=\dfrac{1}{2}+\dfrac{1}{2}.(-80).\dfrac{1}{100}-\dfrac{10}{100}\\
=\dfrac{1}{2}-40.\dfrac{1}{100}-\dfrac{1}{10}\\
=\dfrac{1}{2}-\dfrac{2}{5}-\dfrac{1}{10}\\
=\dfrac{5}{10}-\dfrac{4}{10}-\dfrac{1}{10}\\
=\dfrac{5-4-1}{10}=0$
b) 75%-$3\dfrac{1}{2}+0,5:\dfrac{5}{12}$
$=\dfrac{75}{100}-\dfrac{7}{2}+\dfrac{1}{2}.\dfrac{12}{5}\\
=\dfrac{3}{4}-\dfrac{7}{2}+\dfrac{6}{5}\\
=\dfrac{15}{20}-\dfrac{70}{20}+\dfrac{24}{20}\\
=\dfrac{15-70+24}{20}\\
=\dfrac{-31}{20}$
2)
$a) x-1\dfrac{1}{2}x=5.\dfrac{1}{100}\\
\Leftrightarrow x-\dfrac{3}{2}x=\dfrac{1}{20}\\
\Leftrightarrow \dfrac{2}{2}x-\dfrac{3}{2}x=\dfrac{1}{20}\\
\Leftrightarrow \dfrac{-1}{2}x=\dfrac{1}{20}\\
\Leftrightarrow x=\dfrac{1}{20}.(-2)=\dfrac{-1}{10}\\
b)
\dfrac{75}{100}x-\dfrac{2}{5}x=\dfrac{3}{10}\\
\Leftrightarrow \dfrac{3}{4}x-\dfrac{2}{5}x=\dfrac{3}{10}\\
\Leftrightarrow \dfrac{15}{20}x-\dfrac{8}{20}x=\dfrac{3}{10}\\
\Leftrightarrow \dfrac{7}{20}x=\dfrac{3}{10}\\
\Leftrightarrow x=\dfrac{3}{10}.\dfrac{20}{7}=\dfrac{6}{7}$
