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yx1/2+y-yx7/2=21-yx1/4 =>yx1/2+y-yx7/2+yx1/4=21
=>y x (1/2+1-7/2+1/4)=21 => y x (-7/4)=21 =>y=21:(-7/4)=21 x (4/-7)=-12
\(\frac{2}{3}\times\frac{1}{5}+\frac{3}{10}\times\frac{2}{3}+\frac{4}{6}\times\frac{1}{2}\)
\(=\frac{2}{3}\times\frac{1}{5}+\frac{3}{10}\times\frac{2}{3}+\frac{2}{3}\times\frac{1}{2}\)
\(=\frac{2}{3}\times\left(\frac{1}{5}+\frac{3}{10}+\frac{1}{2}\right)\)
\(=\frac{2}{3}\times\frac{10}{10}\)
\(=\frac{2}{3}\)
X × 2 + X × 3 + X × 4 + X = 2130.
= X × 2 + X × 3 + X × 4 + X × 1 = 2130
= X × ( 2 + 3 + 4 + 1 ) = 2130
= X × 10 = 2130
X = 2130 : 10
X = 213
HT NHA
2/3 +5/9 - 3/4 =17/36
2/7 :2/3 -1/7 = 2/7
2/5 * 1/4 :3/8 = 4/15 nha bạn
2 - \(\frac{5}{7}\)+\(\frac{9}{21}\)= \(\frac{9}{7}\)+\(\frac{9}{21}\)= \(\frac{12}{7}\)
\(\frac{5}{8}\): 3 x\(\frac{24}{25}\)= \(\frac{5}{24}\)x \(\frac{24}{25}\)= \(\frac{1}{5}\)
mk nhanh nhất tk mk nha
2/3 x 3/4 x 4/5 : 1/5 = 6/12 x 4/5 :1/5 = 24/60 :1/5 = 4/10 : 1/5 = 4/10 x 5/1 = 20/10 = 2
2/5 x 3/4 x 5/6 : 3/4 = 6/20 x 5/6 : 3/4 = 3/10 x 5/6 : 3/4 = 15/60 : 3/4 = 1/4 : 3/4 = 1/4 x 4/3 = 4/12 = 1/3
k cho mk nha!
a; 60 \(\times\) (\(\dfrac{7}{12}\) + \(\dfrac{4}{15}\))
= 60 \(\times\) \(\dfrac{7}{12}\) + 60 \(\times\) \(\dfrac{4}{15}\)
= 35 + 16
= 51
\(\frac{1}{2}x+x-\frac{7}{2}x=21-\frac{1}{4}x\)
\(-2x=21-\frac{1}{4}x\)
\(-2x+\frac{1}{4}x=21\)
\(\frac{-7}{4}x=21\)
\(x=-12\)