Bài 1:
a) -$\frac{10}{11}$ . $\frac{8}{9}$ + $\frac{7}{18}$ . $\frac{10}{11}$
= $\frac{10}{11}$ . (-$\frac{8}{9}$) + $\frac{7}{18}$ . $\frac{10}{11}$
= $\frac{10}{11}$ . (-$\frac{8}{9}$ + $\frac{7}{18}$)
= $\frac{10}{11}$ . ($\frac{-16}{18}$ + $\frac{7}{18}$)
= $\frac{10}{11}$ . $\frac{9}{18}$
= $\frac{10}{11}$ . $\frac{1}{2}$
= $\frac{5}{11}$
b) 11$\frac{1}{4}$ - (2$\frac{5}{7}$ + 5$\frac{1}{4}$)
= 11$\frac{1}{4}$ - 2$\frac{5}{7}$ - 5$\frac{1}{4}$
= 11$\frac{1}{4}$ - 5$\frac{1}{4}$ - 2$\frac{5}{7}$
= 6 - $\frac{19}{7}$
= $\frac{42}{7}$ - $\frac{19}{7}$
= $\frac{23}{7}$
Bài 2:
0,5x - $\frac{2}{3}$x = $\frac{7}{12}$
(0,5 - $\frac{2}{3}$)x = $\frac{7}{12}$
($\frac{1}{2}$ - $\frac{2}{3}$)x = $\frac{7}{12}$
($\frac{3}{6}$ - $\frac{4}{6}$)x = $\frac{7}{12}$
$\frac{-1}{6}$x = $\frac{7}{12}$
x = $\frac{7}{12}$ : $\frac{-1}{6}$
x = $\frac{7}{12}$ . (-6)
x = $\frac{-7}{2}$
Vậy x = $\frac{-7}{2}$
