a) $- \frac{12}{5} - \frac{7}{5} = - \frac{19}{5} = -3,8$
b) $(-16.5) + 29.5 + (-3.5) = 9,5$
c) $\frac{2}{11} \cdot \frac{3}{4} + \frac{2}{11} \cdot \frac{7}{8} - \frac{2}{11} \cdot \frac{4}{16} = \frac{6}{44} + \frac{14}{88} - \frac{8}{176} = \frac{3}{22} + \frac{7}{44} - \frac{1}{22} = \frac{5}{22}$
a) \(\dfrac{-12}{5}-\dfrac{7}{5}\) b) ( -16,5) + 29,5 + (-3,5) c) \(\dfrac{2}{11}.\dfrac{3}{4}+\dfrac{2}{11}.\dfrac{7}{8}-\dfrac{2}{11}.\dfrac{4}{16}\)
= \(\dfrac{-12-7}{5}\) = (16,5) + 29,5 - 3,5 = \(\dfrac{2}{11}.\left(\dfrac{3}{4}+\dfrac{7}{8}-\dfrac{4}{16}\right)\)
= \(\dfrac{-19}{5}\) = 29,5 - ((16,5) + 3,5) = \(\dfrac{2}{11}.\left(\dfrac{12}{16}+\dfrac{14}{16}-\dfrac{4}{16}\right)\)
= 29,5 - 20 = \(\dfrac{2}{11}.\dfrac{22}{16}\)
= 9,5 = \(\dfrac{2}{11}.\dfrac{11}{8}\)
= \(\dfrac{1.1}{1.4}\)
= \(\dfrac{1}{4}\)
d) \(\dfrac{4}{7}.x+\dfrac{2}{3}=\dfrac{-1}{5}\)
\(\dfrac{4}{7}.x\) \(=\dfrac{-1}{5}-\dfrac{2}{3}\)
\(\dfrac{4}{7}.x\) = \(\dfrac{-3}{15}-\dfrac{10}{15}\)
\(\dfrac{4}{7}.x\) \(=\dfrac{-13}{15}\)
\(x\) \(=\dfrac{-13}{15}:\dfrac{4}{7}\)
\(x\) \(=\dfrac{-13}{15}.\dfrac{7}{4}\)
\(x\) \(=\dfrac{-91}{60}\)
Vậy \(x=\dfrac{-91}{60}\)