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a) \(\frac{13+x}{20}=\frac{3}{4}\)
\(\Rightarrow\frac{13+x}{20}=\frac{15}{20}\)
\(\Rightarrow13+x=15\)
\(\Rightarrow\) \(x=15-13\)
\(\Rightarrow\)\(x=2\)
b)\(\frac{23-x}{25}=\frac{4}{5}\)
\(\Rightarrow\frac{23-x}{25}=\frac{20}{25}\)
\(\Rightarrow23-x=20\)
\(\Rightarrow\) \(x=23-20\)
\(\Rightarrow\) \(x=3\)
a, 13+x/20= 3/4
Suy ra: ( 13+x). 4= 20.3
Suy ra: (13+x).4=60
Suy ra: 13+x=60:4
Suy ra: 13+x=15
Suy ra: x=15-13
Suy ra: x=2
Vậy x=2
a ) \(1\frac{1}{2}+2\frac{1}{3}+3\frac{1}{6}-5\)
\(=\frac{3}{2}+\frac{7}{3}+\frac{19}{6}-\frac{5}{1}\)
\(=\frac{9}{6}+\frac{14}{6}+\frac{19}{6}-\frac{30}{6}\)
\(=\frac{23}{6}+\frac{19}{6}-\frac{30}{6}\)
\(=\frac{42}{6}-\frac{30}{6}\)
\(=\frac{12}{6}=2\)
b ) \(2\frac{2}{3}\times3\frac{3}{4}\div4\frac{4}{5}\)
\(=\frac{8}{3}\times\frac{15}{4}\div\frac{24}{5}\)
\(=\frac{120}{12}\div\frac{24}{5}\)
\(=\frac{120}{12}\times\frac{5}{24}\)
\(=\frac{600}{288}=\frac{25}{12}\)
c ) \(4\frac{1}{5}+5\frac{1}{3}-2\frac{2}{3}\times3\frac{1}{5}+\frac{9}{25}\div\frac{9}{20}\)
\(=\frac{21}{5}+\frac{16}{3}-\frac{8}{3}\times\frac{16}{5}+\frac{9}{25}\div\frac{9}{20}\)
\(=\frac{63}{15}+\frac{80}{15}-\frac{128}{15}+\frac{9}{25}\times\frac{20}{9}\)
\(=\frac{143}{15}-\frac{128}{15}+\frac{180}{225}\)
\(=\frac{15}{15}+\frac{12}{15}\)
\(=\frac{27}{15}=\frac{9}{5}\)
a)\(\frac{8}{13}+\frac{4}{9}+\frac{1}{3}+\frac{5}{13}+3\)
\(=\left(\frac{8}{13}+\frac{5}{13}\right)+\left(\frac{4}{9}+\frac{1}{3}\right)+3\)
\(=1+\left(\frac{4}{9}+\frac{3}{9}\right)+3\)
\(=1+\frac{7}{9}+3\)
\(=1+3+\frac{7}{9}\)
\(=4\frac{7}{9}\)
\(=\frac{43}{9}\)
b)\(\frac{8}{5}\cdot\frac{4}{7}+\frac{4}{7}\cdot\frac{2}{5}-1\)
\(=\frac{4}{7}\cdot\left(\frac{8}{5}+\frac{2}{5}\right)-1\)
\(=\frac{4}{7}\cdot2-1\)
\(=\frac{8}{7}-1\)
\(=\frac{1}{7}\)
a) \(\frac{8}{13}+\frac{4}{9}+\frac{1}{3}+\frac{5}{13}+3\)
\(=\left(\frac{8}{13}+\frac{5}{13}\right)+\left(\frac{4}{9}+\frac{3}{9}\right)+3\)
\(=1+\frac{7}{9}+3=4\frac{7}{9}\)
b)\(\frac{8}{5}.\frac{4}{7}+\frac{4}{7}.\frac{2}{5}-1\)
\(=\frac{4}{7}.\left(\frac{8}{5}+\frac{2}{5}\right)-1\)
\(=\frac{4}{7}.2-1\)
\(=\frac{8}{7}-\frac{7}{7}=\frac{1}{7}\)
\(\frac{13+x}{20}=\frac{3}{4}=\frac{15}{20}\)
=> 13+x=15
=> x=15-13
=> x=2
\(\frac{23-x}{25}=\frac{4}{5}=\frac{20}{25}\)
=> 23-x=20
=> x=23-20
=> x=3
\(\frac{13+x}{20}=\frac{3}{4}=\frac{15}{20}\)
=>13+x=15
=>x=2
\(\frac{23-x}{25}=\frac{4}{5}=\frac{20}{25}\)
=>23-x=20
=>x=3