( 7/15 + 8/15 ) + ( 3/4 + 1/4 )

= 1 + 1

= 2

=(7/15+8/15)+(3/4+1/4)=1+1=2

\(25^{2n}:5^n=125\)

\(\left(5^2\right)^{2n}:5^n=5^3\)

\(5^{2.2n}:5^n=5^3\)

\(5^{4n-n}=5^3\)

\(5^{3n}=5^3\)

\(3n=3\)

\(n=3:3\)

\(n=1\)

\(\Leftrightarrow5^{4n}:5^n=125\)

=>5^3n=5^3

=>3n=3

=>n=1

0,8 : 2,5

= 0,32

A = \(\frac{2}{3}+\left(\frac{5}{7}+\frac{-2}{3}\right)\)

   = \(\frac{2}{3}+\frac{1}{21}\)

   = \(\frac{5}{7}\)

hok thêm ak?

A,

0,7.0,25.2,4=0,42

B,

6,33+9,48+3,67+2,52

=(6,33+3,67)+(9,48+2,52)

=10+12

=22

C,

2,5.12,5.0,8.4

=100

D,

20,09-(3,49+6,51)

=20,09-10

=10,09

a) 7.3x8.3+3.8x7.3-5x7.3x0.4

=7.3x(8.3+3.8-5x0.4)

=7.3x10.1

=73.73

b)\(\frac{1}{10}:0.1-\frac{1}{8}:0.125+\frac{1}{2}:0.5-\frac{1}{4}:0.25\)

=1-1+1-1=0

c)\(\left(\frac{2727}{3636}+\frac{1212}{5454}\right)\times\left(\frac{9}{70}\right)=\left(\frac{3}{4}+\frac{2}{9}\right)\times\left(\frac{9}{70}\right)\)

=\(\frac{35}{36}\times\frac{9}{70}\)=\(\frac{1}{8}\)

d) 120x999+\(\frac{120}{5\times2.5\times125\times4\times0.8}\)

=120x999+\(\frac{120}{5000}\)

=120x999+\(\frac{3}{125}\)

=119880.024

a 73,73

b1/8

c 119880,024

đúng nha 

k mình nha mn

   2,5 x 2,7 x 0,8 : 0,25

= (2,5 : 0,25) x 2,7 x 0,8

= 10 x 2,7 x 0,8

= 27 x 0,8

= 21,6