Bài 1:
b) $\frac{5}{6}$ + $\frac{4}{7}$ = $\frac{35 + 24}{42}$ = $\frac{59}{42}$
$\frac{7}{11}$ +$\frac{15}{33}$ = $\frac{27 + 15}{33}$ = $\frac{14}{11}$
$\frac{1}{2}$ + $\frac{2}{3}$ + $\frac{5}{6}$ = $\frac{3 + 4 + 5}{6}$ = 2
$\frac{8}{15}$ + $\frac{7}{10}$ + $\frac{2}{3}$ = $\frac{16 + 21 + 20}{30}$ = $\frac{19}{10}$
Bài 2:
b) x - $\frac{3}{10}$ = $\frac{9}{10}$ + $\frac{18}{10}$
⇔ x - $\frac{3}{10}$ = $\frac{27}{10}$
⇔ x = $\frac{27 + 3}{10}$
⇔ x = 3