a) \(\dfrac{7}{11} + \dfrac{3}{4} + \dfrac{4}{11} + \dfrac{1}{4}\)
\( = \left( \dfrac{7}{11} + \dfrac{4}{11}\right) + \left(\dfrac{3}{4} + \dfrac{1}{4}\right)\)
\(= \dfrac{11}{11} + \dfrac{4}{4} = 1 + 1 =2\)
b) \(\dfrac{72}{99} - \dfrac{28}{99} - \dfrac{14}{99}\)
\( = \dfrac{72}{99} - \left(\dfrac{28}{99} +\dfrac{14}{99}\right)\)
\(= \dfrac{72}{99} - \dfrac{42}{99} = \dfrac{30}{99} = \dfrac{10}{33}\)
c) \(69,78 + 35,97 +30,22 \)
\(= (69,78 + 30,22) + 35,97 \)
\(= 100 + 35,97 = 135,97\)
d) \(83,45 - 30,98 - 42,47 \)
\(= 83,45 - (30,98 + 42,47) \)
\(= 83,45 - 73,45 = 10\)
