7,5.x: ( 8-5 195\315 )= 2 13/15
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\(x+x:5.7,5+x:2.9=315\)
\(x+x.1,5+x.4,5=315\)
\(x.\left(1+1,5+4,5\right)=315\)
\(x.7=315\)
\(x=315:7=45\)
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X + X : 5 x 7,5 + X : 2 x 9 = 315
X + X x 1,5 + X x 4,5 = 315
X x ( 1 + 1 , 5 + 4,5 ) = 315
X x 7 = 315
X = 45
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Tìm x, biết:
x + x/5 . 7,5 + x/2 . 9 = 315
=> x + (7,5/5).x + (9/2).x = 315
=> x + 1,5x + 4,5x = 315
=> x.(1 + 1,5 + 4,5) = 315
=> x.7 = 315
=> x = 315/7
=> x = 45
Vậy x = 45
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2: \(=\dfrac{-2}{75}+\dfrac{5}{39}=\dfrac{33}{325}\)
3: \(=\dfrac{6}{11}\left(\dfrac{4}{9}+\dfrac{5}{9}\right)=\dfrac{6}{11}\)
4: \(=\dfrac{7}{19}\left(\dfrac{5}{13}+\dfrac{8}{13}-1\right)=-2\cdot\dfrac{7}{19}=-\dfrac{14}{19}\)
5: \(=\dfrac{2}{7}\left(\dfrac{4}{23}-\dfrac{27}{23}+1\right)=0\)
6: \(=\dfrac{3}{8}\left(\dfrac{3}{7}+\dfrac{4}{7}\right)+\dfrac{11}{8}=\dfrac{3}{8}+\dfrac{11}{8}=\dfrac{14}{8}=\dfrac{7}{4}\)