Bài 3: Tính:

a) \(\frac{2}{3}\) + \(\frac{5}{2}\) - \(\frac{3}{4}\) ;                 \(\frac{2}{5}\) x \(\frac{1}{2}\) : \(\frac{1}{3}\) ;         \(\frac{2}{9}\) : \(\frac{2}{9}\) x \(\frac{1}{2}\) .

b) \(\frac{4}{5}\) - \(\frac{1}{2}\)  + \(\frac{1}{3}\) ;                \(\frac{1}{2}\)  x \(\frac{1}{3}\)  + \(\frac{1}{4}\) ;       \(\frac{2}{7}\) :  \(\frac{2}{3}\) - \(\frac{1}{7}\)

Lời Giải:

Bài 3:

a) \(\frac{2}{3}\) + \(\frac{5}{2}\) - \(\frac{3}{4}\) = \(\frac{8}{12}\) + \(\frac{30}{12}\) - \(\frac{9}{12}\) = \(\frac{38}{12}\) - \(\frac{9}{12}\) = \(\frac{29}{12}\)

\(\frac{2}{5}\) x \(\frac{1}{2}\) : \(\frac{1}{3}\) = \(\frac{1}{5}\) : \(\frac{1}{3}\) = \(\frac{1}{5}\) x \(\frac{3}{1}\) = \(\frac{3}{5}\)

\(\frac{2}{9}\) : \(\frac{2}{9}\) x \(\frac{1}{2}\) = \(\frac{2}{9}\) x \(\frac{9}{2}\) x \(\frac{1}{2}\)  = 1 x \(\frac{1}{2}\)  = \(\frac{1}{2}\)

b)  \(\frac{4}{5}\) - \(\frac{1}{2}\)  + \(\frac{1}{3}\)  = \(\frac{24}{30}\) - \(\frac{15}{30}\) + \(\frac{10}{30}\) = \(\frac{9}{30}\) + \(\frac{10}{30}\) = \(\frac{19}{30}\)

\(\frac{1}{2}\)  x \(\frac{1}{3}\)  + \(\frac{1}{4}\) = \(\frac{1}{6}\) + \(\frac{1}{4}\) = \(\frac{2}{12}\) + \(\frac{3}{12}\) = \(\frac{5}{12}\)

\(\frac{2}{7}\) :  \(\frac{2}{3}\) - \(\frac{1}{7}\) = \(\frac{2}{7}\) x \(\frac{3}{2}\) -  \(\frac{1}{7}\) = \(\frac{3}{7}\) - \(\frac{1}{7}\) = \(\frac{2}{7}\)