\(1,28\cdot5+1,28:0,25+1,28\)

\(=1,28\cdot5+1,28\cdot4+1,28\)

\(=1,28\left(5+4+1\right)\)

\(=1,25\cdot10=12,5\)

1,28:0,125+1,28.0,25+1,8.1,75

=1,28.\(\frac{1}{8}\)+1,28.\(\frac{1}{4}\)+1,8.\(\frac{7}{10}\)

=1,28\(\left(\frac{1}{8}+\frac{1}{4}\right)\)+\(\frac{9}{5}\).\(\frac{7}{10}\)

=1,28\(\left(\frac{1}{8}+\frac{2}{8}\right)\)+\(\frac{63}{50}\)

=\(\frac{32}{25}\cdot\frac{3}{8}+\frac{63}{50}\)

\(=\frac{12}{25}\)

16,12 : 42 ≈ 0,39

1,20 x 15 = 18

16,12:42=0,39

1,2x15=18

3002 \(\times\) 0,58 - 0,58 - 0,58 \(\times\) 2001

= 3002 \(\times\) 0,58 - 0,58 \(\times\) 1 - 0,58 \(\times\) 2001

= 0,58 \(\times\) ( 3002 - 1 - 2001)

= 0,58 \(\times\) 1000

= 580

300 \(\times\) 0,08 + 0,08 \(\times\) 699 + 0,08

= 300 \(\times\) 0,08 + 0,08 \(\times\) 699 + 0,08 \(\times\) 1

= 0,08 \(\times\) ( 300 + 699 + 1)

= 0,08 \(\times\) 1000

= 80

x=3,44

\(x\times12=40+1,28\\ \Rightarrow x\times12=41,28\\ \Rightarrow x=41,28:12\\ \Rightarrow x=3,44\)

3,44

X=16:(1,28:0,5)=6,25

\(16:x=1,28:0,5\\ 16:x=2,56\\ x=16:2,56\\ x=6,25\)

16:x=1,28:0,5

16:x=2,56

     x=16:2,56

     x=6,25

12 : (x * 3) = 1,28 + 2,72

12 : (x * 3) = 4

x * 3 = 12 : 4

x * 3 = 3

x = 3 : 3

x = 1

`->` x = 1.

=1,28(16,5+82,5+1)=1,28x100=128

 1,28x16,5+1,28x82,5+1,28

=1,28x(16,5+82,5+1)

=1,28x100

128

 1,28x16,5+1,28x82,5+1,28

=1,28x(16,5+82,5+1)

=1,28x100

=128

sorry vì hơi chậm nha, em tham khảo bài làm của a: