6.23
a)\(\dfrac{-5}{3}\) - \(\dfrac{-7}{3}\)
=\(\dfrac{-5-\left(-7\right)}{3}\)
=\(\dfrac{2}{3}\)
b)\(\dfrac{5}{6}\)- \(\dfrac{8}{9}\)
=\(\dfrac{5.3}{6.3}\)- \(\dfrac{8.2}{9.2}\)
=\(\dfrac{15}{18}\)-\(\dfrac{16}{18}\)
=\(\dfrac{-1}{18}\)
6.24
A=(-\(\dfrac{3}{11}\)) + \(\dfrac{11}{8}\) - \(\dfrac{3}{8}\) + (-\(\dfrac{8}{11}\))
= [ (-\(\dfrac{3}{11}\)) + (-\(\dfrac{8}{11}\)) ] + ( \(\dfrac{11}{8}\) - \(\dfrac{3}{8}\) )
=\(\dfrac{-11}{11}\) + \(\dfrac{8}{8}\)
= -1 + 1
=0
Tổng phần lương đã chi tiêu và mua quà là:
\(\dfrac{2}{5}\) + \(\dfrac{1}{4}\) = \(\dfrac{8}{20}\) + \(\dfrac{5}{20}\)=\(\dfrac{13}{20}\)
Phần tiền lương còn lại :
1 - \(\dfrac{13}{20}\) = \(\dfrac{20}{20}\) - \(\dfrac{13}{20}\) = \(\dfrac{7}{20}\)
