Tính : B=(4-1/23-56/39-25/47)/(5/69+5/117+5/141)
$ B = \dfrac{1 - \dfrac{1}{23} + 2 - \dfrac{56}{39} + 1 - \dfrac{25}{47} }{\dfrac{5}{69} + \dfrac{5}{117} + \dfrac{5}{141}}\\ \\ = \dfrac{\dfrac{22}{23} + \dfrac{22}{39} + \dfrac{22}{47} }{\dfrac{5}{69} + \dfrac{5}{117} + \dfrac{5}{141}} \\ = \dfrac{22 \left (\dfrac{1}{23} + \dfrac{1}{39} + \dfrac{1}{47} \right )}{\dfrac{5}{3} \left (\dfrac{1}{23} + \dfrac{1}{39} + \dfrac{1}{47} \right )} \\ = \dfrac{22}{\dfrac{5}{3}} \\ = \dfrac{66}{5} $