a, $10101.(\frac{5}{111111}+\frac{5}{222222}-\frac{4}{3.7.11.13.37})$
= $10101.(\frac{5}{11.10101}+\frac{5}{22.10101}-\frac{4}{2.10101})$
= $\frac{5}{11}+\frac{5}{22}-\frac{4}{11}$
= $\frac{7}{22}$
b, $\frac{150.(1252-41)}{(1352-41).(150-15)}= \frac{150}{150-15)}= \frac{10}{9}$
$\frac{2400:48-250}{350-3600:12}=\frac{-53}{12}$
⇒ $\frac{10}{9}<x<\frac{-53}{12}$
⇒ Không có $x$ thỏa mãn