\(\left(-0,35\right)\times\dfrac{3}{14}\times\left(-\dfrac{26}{7}\right)\times\left(-\dfrac{4}{21}\right)\\ =\left(\dfrac{-1,05}{14}\right)\times\left(-\dfrac{26}{7}\right)\times\left(-\dfrac{4}{21}\right)\\ =-\dfrac{109.2}{2058}=\dfrac{91}{1715}\)

\(3\times3-3=6\)

\(34-2:\left(\dfrac{3}{5}-\dfrac{1}{2}\right)\\ =34-2:\left(\dfrac{1}{10}\right)\\ =34-20\\ =14\)

\(\left(x+7\right).34=68\\ x+7=2\\ x=-5\)

a. \(5\dfrac{2}{3}-4\dfrac{3}{8}\\ =\dfrac{17}{3}-\dfrac{35}{8}\\ =\dfrac{31}{24}\)

b.  \(2\dfrac{3}{8}-1\dfrac{1}{4}=\dfrac{19}{8}-\dfrac{5}{4}=\dfrac{9}{8}\)

c. \(\dfrac{1}{2}+\dfrac{3}{2}:\dfrac{1}{2}=\dfrac{1}{2}+3=\dfrac{7}{2}\)

\(\dfrac{1}{3}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{24}=\dfrac{8}{24}+\dfrac{4}{24}+\dfrac{2}{24}+\dfrac{1}{24}\\ =\dfrac{5}{8}\)

f. \(M=3,5x^2y-2xy^2+1,5x^2y+2xy+3xy^2\\ M=5x^2y+xy^2+2xy\)

Biến x bậc 4 , biến y bậc 4

\(N=2x^2y+3,2xy+xy^2-4xy^2-1,2xy\\ N=2x^2y+2xy-3xy^2\)

Biến x bậc 4 , biến y bậc 4

g. \(M-N=5x^2y+xy^2+2xy-2x^2y-2xy+3xy^2\\ M-N=3x^2y+4xy^2\)

a. \(5x^2yz\left(8xy^2z\right)\\ =40x^3y^4z^2\)

Bậc : 3,4,2

b. \(15xy^2z\left(-\dfrac{4}{3}x^2yz^3\right).2xy\\ =-40x^4y^4z^4\)

Bậc : 4

\(20^{3x}=20^{13}:\left(4.5\right)^4\\ 20^{3x}=20^{13}:20^4\\ 20^{3x}=20^9\\ 3x=9\\ x=3\)