a: \(A=\dfrac{1}{9}:\dfrac{1}{9}:\left(\dfrac{10+7}{15}:\dfrac{12-5}{30}\right)\)

\(=1:\left(\dfrac{17}{15}\cdot\dfrac{30}{7}\right)=1:\dfrac{34}{7}=\dfrac{7}{34}\)

b: \(=\left(5.6+0.64\right)\cdot1.25\cdot\dfrac{19}{3}+31.64\)

\(=\dfrac{39}{5}\cdot\dfrac{19}{3}+\dfrac{791}{25}=\dfrac{2026}{25}\)

a: \(A=\left(0+1\right):\left(\dfrac{2}{3}+\dfrac{7}{6}-\dfrac{1}{6}\right)=1:\dfrac{5}{3}=\dfrac{3}{5}\)

b: \(B=\left[0.8\cdot15\right]\cdot\left[1.25\cdot\dfrac{19}{3}\right]+31.64=15\cdot\dfrac{95}{12}+31.64=150.39\)

A = (  0,87 +6,4 ).(1,25.7 - 4/5.1,25)+31,64

A= 7,2.7,75+31,64

A=55,8+31,64

A=87,44

(0,87 + 6,4) . (1,25 . 7 - 4/5 . 1,25) + 31,64

= 7,27 . (8,75 - 1) + 31,64

= 7,27 . 7,75 + 31,64

= 56,3425 + 31,64

= 87,9825

879825

A=ghi laị biểu thức 

A=(0,8*7+0,8*0,8)*(1,25*7-1,25*4/5)+31,64

A=[0,8*(7+0,8)]*[1,25*(7-4/5)]+31,64

A=(0,8*7,8)*(1,25*6,2)+31,+31,64

A=6,24*7,75+31,64

A=48,36+31,64

A=80

Ta có :

A = \(\left[0,8.7+\left(0,8\right)^2\right].\left(1,25.7-\dfrac{4}{5}.1,25\right)+31,64\)

A = \(\left[0,8.\left(7+0,8\right)\right].\left[1,25.\left(7-\dfrac{4}{5}\right)\right]+31,64\)

A = \(\left(0,8.7,8\right)\left(1,25.6,2\right)+31,64\)

A = 6,24 . 7,75 + 31,64

A = 48,36 + 31,64

A = 80

B = \(\dfrac{\left(1,09-1,29\right).\dfrac{5}{4}}{\left(18,9-16,25\right).\dfrac{8}{9}}\)

B= \(\dfrac{\dfrac{4}{5}.\dfrac{5}{4}}{\dfrac{9}{4}.\dfrac{8}{9}}\)

B = \(\dfrac{1}{2}\)

Vậy A gấp B : 80 :\(\dfrac{1}{2}\) = 160 (lần)

Ta có : A = [0,8.7 + (0,8)²](1,25.7 - (4/5).1,25)+31,64

= 0,8.(7 + 0,8).1,25 (7 - 0,8)+ 31,64

= 0,8.7,8.1,25.6,2 + 31,64

= 1.48,36 + 31,64 = 80

Ta có: A : B = 80 : (1/2) = 80.(2/1)=160

Vậy A gấp B là 160 lần