Giải thích các bước giải:
a/ $$\frac{-17}{30}-\frac{11}{-15}+\frac{-7}{12}$$
$$=\frac{-17}{30}-\frac{-11}{15}+\frac{-7}{12}$$
$$=\frac{-34}{60}-\frac{-44}{60}+\frac{-35}{60}$$
$$=\frac{10}{60}+\frac{-35}{60}$$
$$=\frac{-5}{12}$$
b/ $$\frac{-5}{9}+\frac{5}{9}:(\frac{1}{3}+\frac{1}{12})$$
$$=\frac{-5}{9}+\frac{5}{9}:(\frac{4}{12}+\frac{1}{12})$$
$$=\frac{-5}{9}+\frac{5}{9}:\frac{5}{12}$$
$$=\frac{-5}{9}+\frac{5}{9}.\frac{12}{5}$$
$$=\frac{-5}{9}+\frac{4}{3}$$
$$=\frac{-5}{9}+\frac{12}{9}$$
$$=\frac{7}{9}$$
c/ $$\frac{-7}{25}.\frac{11}{13}+\frac{-7}{25}.\frac{2}{13}-\frac{18}{25}$$
$$=\frac{-7}{25}.(\frac{11}{13}+\frac{2}{13})-\frac{18}{25}$$
$$=\frac{-7}{25}.1-\frac{18}{25}$$
$$=\frac{-7}{25}-\frac{18}{25}$$
$$=-1$$
d/ $$(\frac{-2}{3}+\frac{1}{4}+\frac{1}{6}).\frac{-24}{10}$$
$$=(\frac{-8}{12}+\frac{3}{12}+\frac{2}{12}).\frac{-12}{5}$$
$$=\frac{-1}{4}.\frac{-12}{5}$$
$$=\frac{3}{5}$$
e/ $$\frac{1}{4}+\frac{3}{4}.(\frac{1}{2}-\frac{2}{3})$$
$$=\frac{1}{4}+\frac{3}{4}.(\frac{3}{6}-\frac{4}{6})$$
$$=\frac{1}{4}+\frac{3}{4}.\frac{-1}{6}$$
$$=\frac{1}{4}+\frac{-1}{8}$$
$$=\frac{2}{8}+\frac{-1}{8}$$
$$=\frac{1}{8}$$
