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\(a,\dfrac{x}{4}=\dfrac{15}{20}\\ \Rightarrow\dfrac{x}{4}=\dfrac{3}{4}\\ \Rightarrow x=3\\ b,\dfrac{15}{x}=\dfrac{25}{35}\\ \Rightarrow\dfrac{15}{x}=\dfrac{5}{7}\\ \Rightarrow\dfrac{15}{x}=\dfrac{15}{21}\\ \Rightarrow x=21\\ c,\dfrac{x}{5}=\dfrac{26}{65}\\ \Rightarrow\dfrac{x}{5}=\dfrac{2}{5}\\ \Rightarrow x=2\\ d,\dfrac{3}{x}=\dfrac{51}{85}\\ \Rightarrow\dfrac{3}{x}=\dfrac{3}{5}\\ \Rightarrow x=5\)
a,x4=1520⇒x4=34⇒x=3b,15x=2535⇒15x=57⇒15x=1521⇒x=21c,x5=2665⇒x5=25⇒x=2d,3x=5185⇒3x=35⇒x=5
( 12 x 13 + 14 x 15 + ... + 24 x 25 + 26 x 27 ) x ( 14 + 6 - 10 + 5 - 3 x 5 )
= ( 12 x 13 + 14 x 15 + ... + 24 x 25 + 26 x 27 ) x 0
= 0
a) \(\dfrac{2}{3};\dfrac{5}{8};\dfrac{24}{25}\)
b) \(\dfrac{10}{15};\dfrac{12}{18};\dfrac{18}{27}\)
\(\dfrac{x}{5}=\dfrac{26}{65}\)
\(\dfrac{x}{5}=\dfrac{2}{5}\)
\(x=2\)
______________________________________________
\(\dfrac{3}{x}=\dfrac{51}{85}\)
\(\dfrac{3}{x}=\dfrac{3}{5}\)
`x=5`
a) (26x320+13x640):65=(8320+13x640):65
= (8320+8320):65
=16640:65
=256
\(\dfrac{x}{5}=\dfrac{26}{65}\)
\(\Leftrightarrow65x=130\)
\(\Leftrightarrow x=2\)
\(\dfrac{3}{x}=\dfrac{51}{85}\)
\(\Leftrightarrow51x=255\)
\(\Leftrightarrow x=5\)
`x/5=26/65`
`65xx x=5xx26`
`65xx x=130`
`x=130:65=2`
`3/x=51/85`
`51xx x=3xx85`
`51xx x=255`
`x=255:51=5`
a)\(\frac{1}{3}< \frac{6}{x}< \frac{3}{10}\)
\(\frac{6}{18}< \frac{6}{x}< \frac{6}{20}\)
=>x=19
b)\(\frac{1}{3}< \frac{x}{15}< \frac{1}{5}\)
\(\frac{5}{15}< \frac{x}{15}< \frac{3}{15}\)
=>x=4
\(a,\dfrac{x}{3}=\dfrac{10}{15}\\ \Rightarrow\dfrac{x}{3}=\dfrac{2}{3}\\ \Rightarrow x=2\\ b,\dfrac{x}{5}=\dfrac{26}{65}\\ \Rightarrow\dfrac{x}{5}=\dfrac{2}{5}\\ \Rightarrow x=2\)
a, \(\dfrac{x}{3}=\dfrac{10}{15}\Leftrightarrow\dfrac{5x}{15}=\dfrac{10}{15}\Rightarrow x=2\)
b, \(\dfrac{x}{5}=\dfrac{26}{65}\Leftrightarrow\dfrac{13x}{65}=\dfrac{26}{65}\Rightarrow x=2\)