\(a,\left(x-35\right)-120=0\)

\(x-35=0+120=120\)

\(x=120+35=155\)

\(b,124+\left(118-x\right)=217\)

\(118-x=217-124=93\)

\(x=118-93=25\)

\(c,156-\left(x+61\right)=82\)

\(x+61=156-82=74\)

\(x=74-61=13\)

bài 6

\(a,\dfrac{1}{2}+\dfrac{-3}{5}=\dfrac{5}{10}+\dfrac{-6}{10}=\dfrac{-1}{10}\)

\(b,\dfrac{5}{2}+\dfrac{-9}{8}=\dfrac{20}{8}+\dfrac{-9}{8}=\dfrac{11}{8}\)

\(c,\dfrac{5}{2-15}+\dfrac{6}{8}=\dfrac{5}{-13}+\dfrac{6}{8}=-\dfrac{40}{104}+\dfrac{78}{104}=\dfrac{19}{52}\)

\(d,\dfrac{15}{25}+\dfrac{-27}{12}=\dfrac{3}{15}+\dfrac{-9}{4}=\dfrac{12}{60}+\dfrac{-135}{60}=\dfrac{-123}{60}=\dfrac{-41}{20}\)

Câu 7

\(a,\dfrac{5}{3}+\left(7+\dfrac{-5}{3}\right)=\dfrac{5}{3}+7+\dfrac{-5}{3}=\left(\dfrac{5}{3}+\dfrac{-5}{3}\right)+7=7\)

\(b,\dfrac{-7}{31}+\left(\dfrac{24}{17}+\dfrac{7}{31}\right)=\dfrac{-7}{31}+\dfrac{24}{17}+\dfrac{7}{31}=\left(\dfrac{-7}{31}+\dfrac{7}{31}\right)+\dfrac{24}{17}=\dfrac{24}{17}\)

\(c,\dfrac{3}{7}+\left(\dfrac{-1}{5}+\dfrac{-3}{7}\right)=\dfrac{3}{7}+\dfrac{-1}{5}+\dfrac{-3}{7}=\left(\dfrac{3}{7}+\dfrac{-3}{7}\right)+\dfrac{-1}{5}=\dfrac{-1}{5}\)

\(a,\left(\sqrt{8}-3\sqrt{2}+\sqrt{10}\right)\sqrt{2}-\sqrt{5}\)

\(=\left(2\sqrt{2}-3\sqrt{2}+\sqrt{10}\right)\sqrt{2}-\sqrt{5}\)

\(=\left(-1\sqrt{2}+\sqrt{10}\right)\sqrt{2}-\sqrt{5}\)

\(=\left(-\sqrt{2}+\sqrt{10}\right)\sqrt{2}-\sqrt{5}\)

\(=-2\sqrt{2}\sqrt{2}+\sqrt{10}\sqrt{2}-\sqrt{5}\)

\(=-\left(\sqrt{2}\right)^1\sqrt{2}+\sqrt{10}\sqrt{2}-\sqrt{5}\)

\(=-\left(\sqrt{2}\right)^1\left(\sqrt{2}\right)^1+\sqrt{10}\sqrt{2}-\sqrt{5}\)

\(=-\left(\sqrt{2}\right)^2+\sqrt{10}\sqrt{2}-\sqrt{5}\)

\(=-2+\sqrt{10}\sqrt{2}-\sqrt{5}\)

\(=-2+2\sqrt{5}-\sqrt{5}\)

\(=-2+1\sqrt{5}\)

b,\(0.2\sqrt{\left(-10\right)^2.3}+2\sqrt{\left(\sqrt{3}-\sqrt{5}\right)^2}\)

\(=0+2\sqrt{\left(\sqrt{3}-\sqrt{5}\right)^2}\)

\(=2.\left(-\left(\sqrt{3}-\sqrt{5}\right)\right)\)

\(=-2\left(\sqrt{3}-\sqrt{5}\right)\)

\(=-2\sqrt{3}-2.\left(-\sqrt{5}\right)\)

a,\(\left(\dfrac{-10}{3}\right)^5.\left(\dfrac{-6}{5}\right)^4\)

\(=-\dfrac{10^5}{3^5}.\dfrac{6^4}{5^4}\)

\(=-\dfrac{100000}{243}.\dfrac{1296}{625}\)

\(=-\dfrac{2560}{3}\)

b,\(\left(1+\dfrac{2}{3}-\dfrac{1}{4}\right).\left(\dfrac{4}{5}-\dfrac{3}{4}\right)^2\)

\(=\left(\dfrac{12}{12}+\dfrac{8}{12}-\dfrac{3}{12}\right).\left(\dfrac{16}{20}-\dfrac{15}{20}\right)^2\)

\(=\dfrac{17}{12}.\left(\dfrac{1}{20}\right)^2\)

\(=\dfrac{17}{12}.\dfrac{1^2}{20^2}=\dfrac{17}{12}.\dfrac{1}{400}=\dfrac{17}{4800}\)