dễ mà !

lấy 400 : 100 x 4 = 16 ( g )

     16 : 2,5 x 100 = 640 ( g )

     640 - 400 = 240 ( g )

100:100x37=37

binh co 9 vien

a)x+\(\dfrac{5}{6}\)=\(\dfrac{2}{3}-\dfrac{-2}{3}x\)

=>x+\(\dfrac{2}{3}x\)=\(\dfrac{2}{3}\)-\(\dfrac{5}{6}\)

=>\(\dfrac{5}{3}x\)=\(\dfrac{-1}{6}\)

=>\(x\)=\(\dfrac{-1}{10}\)

Vậy \(x=\dfrac{-1}{10}\)

b)1\(\dfrac{2}{5}x\)+\(\dfrac{3}{7}\)=\(\dfrac{-4}{5}-\dfrac{1}{5}x\)

=>\(\dfrac{7}{5}x\)+\(\dfrac{1}{5}x\)=\(\dfrac{-4}{5}-\dfrac{3}{7}\)

=>\(\dfrac{8}{5}x\)=\(\dfrac{-43}{35}\)

=>\(x\)=\(\dfrac{-43}{56}\)

KL:...

c)

=1-\(\dfrac{1}{3}\)

=>\(\dfrac{-2}{3}x\)+\(\dfrac{1}{3}\)=\(\dfrac{2}{3}\)

=>\(\dfrac{-2}{3}x\)=\(\dfrac{1}{3}\)

=>\(x\)=\(\dfrac{-1}{2}\)

KL: