Lời giải:
a.
\(=\frac{31}{23}-\frac{7}{32}-\frac{8}{23}=\frac{31-8}{23}-\frac{7}{32}=1-\frac{7}{32}=\frac{25}{32}\)
b.
\(=\frac{38}{45}-\frac{8}{45}+\frac{17}{51}+\frac{3}{11}=\frac{30}{45}+\frac{17}{51}+\frac{3}{11}\)
\(=\frac{2}{3}+\frac{1}{3}+\frac{3}{11}=1+\frac{3}{11}=\frac{14}{11}\)
c.
\(=\frac{1}{3}+\frac{12}{67}+\frac{13}{41}-\frac{79}{67}+\frac{28}{41}\)
\(=\frac{1}{3}+\frac{12-79}{67}+\frac{13+28}{41}=\frac{1}{3}+\frac{-67}{67}+\frac{41}{41}=\frac{1}{3}+(-1)+1=\frac{1}{3}\)