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\(\dfrac{4\times x}{1\times5}\) + \(\dfrac{4\times x}{5\times9}\) + \(\dfrac{4\times x}{9\times13}\) + \(\dfrac{4\times x}{13\times17}\) = 16
\(x\times\left(\dfrac{4}{1\times5}+\dfrac{4}{5\times9}+\dfrac{4}{9\times13}+\dfrac{4}{13\times17}\right)\) = 16
\(x\) \(\times\) (\(\dfrac{1}{1}\) - \(\dfrac{1}{5}\) + \(\dfrac{1}{5}\) - \(\dfrac{1}{9}\) + \(\dfrac{1}{9}\) - \(\dfrac{1}{13}\) + \(\dfrac{1}{13}\) - \(\dfrac{1}{17}\)) = 16
\(x\) \(\times\) ( \(\dfrac{1}{1}\) - \(\dfrac{1}{17}\)) = 16
\(x\) \(\times\) \(\dfrac{16}{17}\) = 16
\(x\) = 16 : \(\dfrac{16}{17}\)
\(x\) = 17
\(31,6:\left[x-2,75\right]=10\)
\(\Rightarrow\left[x-2,75\right]=31,6:10\)
\(\Rightarrow\left[x-2,75\right]=3,16\)
\(\Rightarrow x=3,16+2,75=5,91\)
31,6 : ( x - 2,75 ) = 10
x - 2,75 = 31,6 : 10
x - 2,75 = 3,16
x = 3,16 + 2,75
x = 5,91
0,75 x X + 0,75 x X + X = 30
X x ( 0,75 + 0,75 + 1 ) = 30
X x 2,5 = 30
X = 30 : 2,5
X = 12
75%xX+3/4xX+X=30
<=>3/4xX+3/4xX+X=30
<=>10/4xX=30
<=>10xX=120
<=>X=120/10=12
Vậy X=12
đổi 75%=3/4.Ta có:
3/4xX+3/4xX+X=30
(3/4+3/4+1)xX=30
5/2 x X=30
X = 30:5/2
X = 12
\(75\%\times x+\frac{3}{4}\times x+x=30\)
\(\frac{3}{4}\times x+\frac{3}{4}\times x+1\times x=30\)
\(\left(\frac{3}{4}+\frac{3}{4}+1\right)\times x=30\)
\(\frac{5}{2}\times x=30\)
\(x=30\div\frac{5}{2}\)
\(x=12\)