Bài 2:
a, $\frac{3}{8}$ + $\frac{1}{2}$ = $\frac{3}{8}$ + $\frac{4}{8}$ = $\frac{7}{8}$
$\frac{8}{9}$ + $\frac{1}{3}$ = $\frac{8}{9}$ + $\frac{3}{9}$ = $\frac{11}{9}$
$\frac{3}{10}$ + $\frac{1}{2}$ = $\frac{3}{10}$ + $\frac{5}{10}$ = $\frac{8}{10}$ = $\frac{4}{5}$
$\frac{3}{2}$ + $\frac{9}{4}$ = $\frac{6}{4}$ + $\frac{9}{4}$ = $\frac{15}{4}$
$\frac{1}{9}$ + $\frac{2}{3}$ = $\frac{1}{9}$ + $\frac{6}{9}$ = $\frac{7}{9}$
b, $\frac{13}{8}$ - $\frac{1}{4}$ = $\frac{13}{8}$ - $\frac{2}{8}$ = $\frac{11}{8}$
$\frac{8}{9}$ - $\frac{1}{18}$ = $\frac{16}{18}$ - $\frac{1}{18}$ = $\frac{15}{18}$ = $\frac{5}{6}$
$\frac{9}{10}$ - $\frac{1}{2}$ = $\frac{9}{10}$ - $\frac{5}{10}$ = $\frac{4}{10}$ = $\frac{2}{5}$
$\frac{3}{2}$ - $\frac{1}{4}$ = $\frac{6}{4}$ - $\frac{1}{4}$ = $\frac{5}{4}$
$\frac{8}{9}$ - $\frac{2}{3}$ = $\frac{8}{9}$ - $\frac{6}{9}$ = $\frac{2}{9}$
Chúc bạn học tốt!!!!