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\(2+\dfrac{5}{9}-\left(\dfrac{21}{-28}+\dfrac{15}{27}\right)\)
\(=\dfrac{23}{9}+\dfrac{3}{4}-\dfrac{5}{9}\)
\(=2+\dfrac{3}{4}=\dfrac{11}{4}\)
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\(2.x-15=11\)
\(2x=11+15\)
\(2x=26\)
\(x=26:2\)
\(x=13\)
\(b,4.\left(2-x\right)-5\left(3-x\right)=-12\)
\(8-4x-15+5x=-12\)
\(x-7=-12\)
\(x=-12+7\)
\(x=-5\)
\(c,\left|x-7\right|+13=25\)
\(\left|x-7\right|=25-13\)
\(\left|x-7\right|=12\)
\(\Rightarrow\orbr{\begin{cases}x-7=12\\x-7=-12\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=19\\x=-5\end{cases}}\)
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\(a,\dfrac{-2}{5}+\dfrac{4}{5}x=\dfrac{3}{5}\)
\(\Rightarrow\dfrac{4x-2}{5}=\dfrac{3}{5}\)
\(\Rightarrow4x-2=3\)
\(\Rightarrow4x=5\)
\(\Rightarrow x=\dfrac{5}{4}\)
\(b,\dfrac{-3}{7}-\dfrac{4}{7}:x=-2\)
\(\Rightarrow\dfrac{-4}{7x}=\dfrac{-11}{7}\)
\(\Rightarrow7x=\dfrac{-4.7}{-11}\)
\(\Rightarrow7x=\dfrac{28}{11}\)
\(\Rightarrow x=\dfrac{4}{11}\)
câu 2 :
\(\dfrac{-55}{132}=\dfrac{\left(-55\right):12}{132:12}=\dfrac{-5}{12}\)
câu 3:
a) < b) <
câu 4 :
a)\(\dfrac{5}{16}-\dfrac{5}{24}=\dfrac{5}{48}\)
b) \(\dfrac{-5}{8}+\dfrac{12}{7}+\dfrac{13}{8}+\dfrac{2}{7}=\left(\dfrac{-5}{8}+\dfrac{13}{8}\right)+\left(\dfrac{12}{7}+\dfrac{2}{7}\right)=1+2=3\)