$\text { Bài 4: }$
$\text { a) }$$\frac {6}{5}$ $\text {+}$ $\frac {4}{3}$
$\text {=}$ $\frac {18}{15}$ $\text {+}$ $\frac { 20}{15}$
$\text {=}$ $\frac {38}{15}$
$\text { b) }$ $\frac {4}{7}$ $\text {×}$ $\frac {9}{6}$
$\text {=}$ $\frac {36}{42}$
$\text {=}$ $\frac {6}{7}$
$\text { c) }$ $\frac {3}{5}$ $\text {:}$ $\frac {3}{7}$ $\text {×}$ $\frac {5}{9}$
$\text {=}$ $\frac {3}{5}$ $\text {×}$ $\frac {7}{3}$ $\text {×}$ $\frac {5}{9}$
$\text {=}$ $\frac {7}{9}$
$\text { d) }$ $\frac {2}{3}$ $\text {+}$ $\frac {5}{8}$ $\text {×}$ $\frac {3}{2}$
$\text {=}$ $\frac {2}{3}$ $\text {+}$ $\frac {15}{16}$
$\text {=}$ $\frac {32}{48}$ $\text {+}$ $\frac {45}{48}$
$\text {=}$ $\frac {77}{48}$
