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.

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

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

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

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

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

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

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

x = 85:1,7 = 50

x = 12,32:0,22 = 56

x = 1,2168 : 0,26 = 4,68

x = 17,2032 :1,28 = 13,44 

a, X x 1,7 = 85  

=> x = 85:1,7 

=>x=50

b, 0,22 x X = 12 , 32    

=>x = 12,32:0,22

=>x= 56

c, X x 0,26 = 1,17 x 1,04

=> x = 1,2168 : 0,26

=>x= 4,68

d, X x 1,28 = 4,48 x 3,84

=>x = 17,2032 :1,28

=>x = 13,44

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

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

Bài 1:

0,5\(x\) - \(\dfrac{2}{3}\)\(x\) = \(\dfrac{7}{12}\)  

\(\dfrac{1}{2}\)\(x\) - \(\dfrac{2}{3}x\)  = \(\dfrac{7}{12}\)

(\(\dfrac{1}{2}-\dfrac{2}{3}\))\(x\) = \(\dfrac{7}{12}\)

- \(\dfrac{1}{6}\)\(x\)         = \(\dfrac{7}{12}\)

     \(x\)         = \(\dfrac{7}{12}\) : (- \(\dfrac{1}{6}\))

     \(x\)        = - \(\dfrac{7}{2}\)

Vậy \(x\) = - \(\dfrac{7}{2}\)

7:2 = 7/2

1,25 x2 = 2,5

1,28 x 4 = 5,12

59:2=59,2

\(7:2=3,5\)

\(1,25\times2=2,5\)

\(1,28\times4=5,12\)

\(59:2=29,5\)

\(7\div2=3\) dư \(1\),  \(7\div2=\dfrac{7}{2}\) hoặc \(7\div2=3,5\)

\(1,25\times2=2,5\)

\(1,28\times4=5,12\)

\(59\div2=29\) dư \(1,59\div2=\dfrac{59}{2}\) hoặc \(59\div2=29,5\)

deadline dí chết hay sao mà căng vậy;-;

\(a,x\times0,26=1,17\times1,04\\ \Rightarrow x\times0,26=1,2168\\ \Rightarrow x=1,2168:0,26\\ \Rightarrow x=4,68\\ b,x\times1,28=4,48\times3,84\\ \Rightarrow x\times1,28=17,2032\\ \Rightarrow x=17,2032:1,28\\ \Rightarrow x=13,44\)

d: =>1,28x=17,2032

hay x=13,44