Bài 1
a) \(\dfrac{3}{8}+\dfrac{5}{8}=\dfrac{8}{8}=1\)
b) \(\dfrac{3}{4}+\dfrac{-7}{16}=\dfrac{12}{16}+\dfrac{-7}{16}=\dfrac{5}{16}\)
c) \(2\dfrac{17}{20}-\dfrac{1}{2}+3\dfrac{3}{20}=\dfrac{57}{20}-\dfrac{1}{2}+\dfrac{63}{20}\)\(=\dfrac{47}{20}+\dfrac{63}{20}=\dfrac{110}{20}=\dfrac{11}{2}\)
d) \(\dfrac{2}{3}-2\dfrac{1}{8}+\dfrac{7}{24}=\dfrac{2}{3}-\dfrac{17}{8}+\dfrac{7}{24}=\dfrac{16}{24}-\dfrac{51}{24}+\dfrac{7}{24}=\dfrac{16-51+7}{24}=\dfrac{-28}{24}=\dfrac{-7}{6}\)
Bài 2 :
a) \(x-\dfrac{7}{4}=3\)
\(x=3+\dfrac{7}{4}\)
\(x=\dfrac{19}{4}\)
b) \(x-\dfrac{1}{2}=\dfrac{4}{16}\cdot\dfrac{8}{3}\)
\(x-\dfrac{1}{2}=\dfrac{2}{3}\)
\(x=\dfrac{2}{3}+\dfrac{1}{2}\)
\(x=\dfrac{5}{6}\)
c) \(\dfrac{15}{11}\div x=\dfrac{45}{22}\)
\(x=\dfrac{15}{11}\div\dfrac{45}{22}\)
\(x=\dfrac{2}{3}\)
d) \(\dfrac{8}{3}-2x=\dfrac{8}{5}-1\)
\(\dfrac{8}{3}-2x=\dfrac{3}{5}\)
\(2x=\dfrac{8}{3}-\dfrac{3}{5}\)
\(2x=\dfrac{31}{15}\)
\(x=\dfrac{31}{15}\div2\)
\(x=\dfrac{31}{30}\)
