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a: Sửa đề: \(\left[\left(6\dfrac{3}{7}-\dfrac{0,75x-2}{0,35}\right)\cdot2.8+1.75\right]\cdot0.05=2.35\)
\(\Leftrightarrow\left(\dfrac{45}{7}-\dfrac{15x-40}{7}\right)\cdot2.8+1,75=47\)
\(\Leftrightarrow\dfrac{45-15x+40}{7}\cdot2,8=45,25\)
\(\Leftrightarrow\dfrac{85-15x}{7}=\dfrac{905}{56}\)
=>8(85-15x)=905
=>680-120x=905
=>120x=-225
hay x=-15/8
b: \(\dfrac{3}{5}-\dfrac{2}{7}< \dfrac{2}{3}x+\dfrac{3}{4}< \dfrac{1}{2}+\dfrac{7}{9}\)
\(\Leftrightarrow\dfrac{11}{35}-\dfrac{3}{4}< \dfrac{2}{3}x< \dfrac{23}{18}-\dfrac{3}{4}\)
\(\Leftrightarrow-\dfrac{61}{140}< \dfrac{2}{3}x< \dfrac{19}{36}\)
\(\Leftrightarrow-\dfrac{183}{280}< x< \dfrac{19}{24}\)
a)x+3/6=7/2
x =7/2-3/6
x =3
b)2,8+(3x-5/6)=2/2/5
14/5+(3x-5/6)=12/5
(3x-5/6)=12/5-14/5
3x+5/6=-2/5
3x =-2/5-5/6
3x =-37/30
x =-37/36:3
x =-37/90
x - 2 =3
x =3+2
x =5
\(6\frac{3}{7}-0,75x-\frac{2}{0,35}\times2,8=10\)
\(\frac{45}{7}-\frac{3}{4}x-\frac{40}{7}\times\frac{28}{10}=10\)
\(\frac{45}{7}-\frac{3}{4}x=10+4\)
\(\frac{3}{4}x=\frac{45}{7}-14\)
\(\frac{3}{4}x=-\frac{53}{7}\)
\(x=-\frac{53}{7}:\frac{3}{4}\)
\(x=\frac{-212}{21}\)