$\text { Đáp án: }$
$\text { a) }$ $\frac {3}{8}$ $–$ $\frac {5}{6}$ $+$ $\frac {1}{4}$
$=$ $\frac {9}{24}$ $–$ $\frac {20}{6}$ $+$ $\frac {6}{24}$
$=$ $\frac {–5}{24}$
$\text { b) }$ $\frac {1}{7}$ $\text { : ( 2 – 1 }$ $\frac {5}{7}$ $\text { ) + }$ $\frac {3}{2}$
$=$ $\frac {1}{7}$ $\text { : ( 2 – }$ $\frac {12}{7}$ $\text { ) + }$ $\frac {3}{2}$
$=$ $\frac {1}{7}$ $:$ $\frac {2}{7}$ $+$ $\frac {3}{2}$
$=$ $\frac {1}{7}$ $.$ $\frac {7}{2}$ $+$ $\frac {3}{2}$
$=$ $\frac {1}{2}$ $+$ $\frac {3}{2}$
$=$ $\frac {3}{3}$ $=$ $1$
