B = 5\(\dfrac{1}{2}\) + \(\dfrac{4}{5}\) - 2,5 + 1,2

B = 5,5 + 0,8 - 2,5 + 1,2

B = (5,5 - 2,5) + (0,8 + 1,2)

B = 3 + 1

B = 4

a)\(\frac{7}{3}.\left( { - 2,5} \right).\frac{6}{7} = \frac{7}{3}.\frac{6}{7}.\left( { - 2,5} \right) = 2.\left( { - 2,5} \right) =  - 5\)

b)

\(\begin{array}{l}0,8.\frac{{ - 2}}{9} - \frac{4}{5}.\frac{7}{9} - 0,2\\ = \frac{4}{5}.\frac{{ - 2}}{9} - \frac{4}{5}.\frac{7}{9}-\frac{2}{10}\\ = \frac{4}{5}.\left( {\frac{{ - 2}}{9} - \frac{7}{9}} \right) -\frac{1}{5}\\ = \frac{4}{5}.\left( { - 1} \right)-\frac{1}{5} \\= \frac{{ - 4}}{5}-\frac{1}{5}\\=\frac{-5}{5}\\=-1.\end{array}\)

= 0,75 + ( 0,8 - 34/15 )

= 0,75 + -22/15

= -43/60

1: 0,35*12,4=0,35*2,4+0,35*10=3,5+0,84=4,34

2: =0,1-2,34=-2,24

3: =5-2,9=2,1

4: \(=2,5\left(10,124-0,124\right)=10\cdot2,5=25\)

5: =-3/7+1/13

=-39/91+7/91

=-32/91

6: =-1/3+1/3=0

a: \(2,5-\frac{-10}{15}=\frac52+\frac23\)

\(=\frac{15}{6}+\frac46=\frac{19}{6}\)

b: \(6,25+\left\lbrack1,75-\left(0,75-2,75\right)\right\rbrack\)

=6,25+1,75+(2,75-0,75)

=8+2

=10

c: \(\frac{8^5\cdot27^2}{3^7\cdot32^4}=\frac{\left(2^3\right)^5\cdot\left(3^3\right)^2}{3^7\cdot\left(2^5\right)^4}=\frac{2^{15}}{2^{20}}\cdot\frac{3^6}{3^7}=\frac{1}{3\cdot2^5}=\frac{1}{96}\)

d: \(2\frac35\cdot\left(-2021\right)-235,91+0,55\cdot94\)

\(=-2021\cdot2,6-235,91+51,7\)

=-5254,6-235,91+51,7

=-5438,81

a) = 5,6 b)=48 c) = 5,6x(4+3+1)=5,6x7=39,2

d)=0

Nhắn k hiểu lắm

1000+26

   23,45 : 12,5 : 0,8

= 23,45 : ( 12,5 x 0,8 )

= 23,45 : 10

= 2,345

   2,5 : 5,6 x 4

= ( 2,5 x 4 ) : 5,6

= 10 : 5,6

= 1.785714285714286

1)23,45 : 12,5 : 0,8

=23,45 : (12,5 x 0,8)

=23,45 : 10

=2,345