Tính bằng phương pháp hợp lí nhất
a) \(\frac{31}{23}\)- ( \(\frac{7}{32}\)+ \(\frac{8}{23}\) )
b) ( \(\frac{1}{3}\)+ \(\frac{12}{67}\)+ \(\frac{13}{41}\)) - ( \(\frac{79}{67}\)- \(\frac{28}{41}\))
c) \(\frac{38}{45}\)- ( \(\frac{8}{45}\)- \(\frac{17}{51}\)- \(\frac{3}{11}\))