Tính a) 5/8 + 2 1/4 . 1 2/3 - 1/4 . 5/6 b) (13 9/11 : 38/49 - 5 2 /11

* Hướng dẫn giải

a) 

$\begin{array}{l}\frac{5}{8}+2\frac{1}{4}.1\frac{2}{3}-\frac{1}{4}.\frac{5}{6}\\ =\frac{5}{8}+\frac{9}{4}.\frac{5}{3}-\frac{5}{24}\\ =\frac{5}{4}.\left(\frac{1}{2}+3-\frac{1}{6}\right)\\ =\frac{5}{4}.\frac{10}{3}=\frac{25}{6}\end{array}$

b)

$\begin{array}{l}\left(13\frac{9}{11}:\frac{38}{49}-5\frac{2}{11}:\frac{38}{49}\right):\left(\frac{49}{38}.\frac{5}{11}\right)\\ =\left\{(13+\frac{9}{11}).\frac{49}{38}-(5+\frac{2}{11}).\frac{49}{38}\right\}:\left(\frac{49}{38}.\frac{5}{11}\right)\\ =\frac{49}{38}.\left(13-5+\frac{9}{11}-\frac{2}{11}\right):\left(\frac{49}{38}.\frac{5}{11}\right)\\ =\frac{49}{38}.\left(8+\frac{7}{11}\right):\left(\frac{49}{38}.\frac{5}{11}\right)\\ =\left(8+\frac{7}{11}\right):\frac{5}{11}=19\end{array}$