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Ta có: a x 2/3 + a x 7/3 = 9
a x (2/3+7/3) = 9
a x 3=9
a=9:3
a=3
a, 7\(\dfrac{3}{5}\) : \(x\) = 5\(\dfrac{4}{15}\) - 1\(\dfrac{1}{6}\)
\(\dfrac{38}{5}\) : \(x\) = \(\dfrac{79}{15}\) - \(\dfrac{7}{6}\)
\(x\) = \(\dfrac{41}{10}\)
\(x\) = \(\dfrac{38}{5}\) : \(\dfrac{41}{10}\)
\(x\) = \(\dfrac{76}{41}\)
b, \(x\) \(\times\) 2\(\dfrac{2}{3}\) = 3\(\dfrac{4}{8}\) + 6\(\dfrac{5}{12}\)
\(x\) \(\times\) \(\dfrac{8}{3}\) = \(\dfrac{7}{2}\) + \(\dfrac{77}{12}\)
\(x\) \(\times\) \(\dfrac{8}{3}\) = \(\dfrac{119}{12}\)
\(x\) = \(\dfrac{119}{12}\)
\(x\) = \(\dfrac{119}{12}\): \(\dfrac{8}{3}\)
\(x\) = \(\dfrac{119}{32}\)
\(\dfrac{3}{5}\) x \(\dfrac{1}{7}\) x 1\(\dfrac{1}{2}\)
= \(\dfrac{3}{35}\) x \(\dfrac{3}{2}\)
= \(\dfrac{9}{70}\)
\(\dfrac{3}{5}\times\dfrac{4}{7}\times1\dfrac{1}{2}\)
\(=\dfrac{3}{5}\times\dfrac{4}{7}\times\dfrac{3}{2}\)
\(=\dfrac{3\times4\times3}{5\times7\times2}\)
\(=\dfrac{3\times2\times3}{5\times7}\)
\(=\dfrac{18}{35}\)
do 5 lần số lớn = 7laanf số bé
nên số lớn băng 7 lần số bé
đén đây thiếu đề vì chưa biết tổng
5/4-yx5/6=-1/12
5/4-y = -1/12:5/6
5/4-y = -1/10
y = 5/4-(-1/10)
y = 27/20
\(\frac{5}{4}-y.\frac{5}{6}=\frac{1}{4}-\frac{1}{3}\)
\(\Rightarrow\frac{5}{4}-y.\frac{5}{6}=-\frac{1}{12}\)
\(\Rightarrow y.\frac{5}{6}=\frac{5}{4}-\left(-\frac{1}{12}\right)\)
\(\Rightarrow y.\frac{5}{6}=\frac{5}{4}+\frac{1}{12}\)
\(\Rightarrow y.\frac{5}{6}=\frac{4}{3}\)
\(\Rightarrow y=\frac{4}{3}:\frac{5}{6}\)
\(\Rightarrow y=\frac{8}{5}\)
Vậy \(y=\frac{8}{5}.\)
a) Ta có: ( x+5) + (2x+7)+(3x+9) = 57
=> (x+2x+3x)+(5+7+9) = 57
=> 6x + 21 = 57
=> 6x = 57 - 21
=> 6x = 36
=> x = 36 : 6
=> x = 6
b) x + 1245 = (3+7+11+...+95)
=> x + 1245 = [(95-3):4+1] x (95+3) : 2
=> x + 1245 = 1176
=> x = 1176 - 1245
=> x = -69
CHÚC BẠN HỌC TỐT
a,\(\frac{2}{5}+\frac{3}{4}=\frac{8+15}{20}=\frac{23}{20}\)
\(\frac{7}{12}-\frac{2}{7}+\frac{1}{12}=(\frac{7}{12}+\frac{1}{12})-\frac{2}{7}\)
\(=\frac{2}{3}-\frac{2}{7}=\frac{14-6}{21}=\frac{8}{21}\)
\(\frac{12}{17}-\frac{5}{17}-\frac{4}{17}=\frac{7}{17}-\frac{4}{17}=\frac{3}{17}\)
b,\(675,39+342,14=1017,53\)
\(563,87+403,13-328,35=638,65\)
2/5+3/4=23/20
7/12-2/7+1/12=8/21
12/17-5/17-4/173/17
675,39+342,14=1017,53
563,87+403,13-328,35=638,65
\(\dfrac{12}{7}:x+\dfrac{2}{3}=\dfrac{7}{5}\)
\(\dfrac{12}{7}:x=\dfrac{7}{5}-\dfrac{2}{3}=\dfrac{11}{15}\)
\(x=\dfrac{12}{7}:\dfrac{11}{15}=\dfrac{180}{77}\)