\(\dfrac{90}{120}=\dfrac{30.3}{30.4}=\dfrac{3}{4}\)

\(\dfrac{15}{25}=\dfrac{5.3}{5.5}=\dfrac{3}{5}\)

\(\dfrac{18}{45}=\dfrac{9.2}{9.5}=\dfrac{2}{5}\)

\(\dfrac{36}{64}=\dfrac{4.9}{4.16}=\dfrac{9}{16}\)

\(\dfrac{32}{72}=\dfrac{8.4}{8.9}=\dfrac{4}{9}\)

\(\dfrac{84}{49}=\dfrac{7.12}{7.7}=\dfrac{12}{7}\)

\(\dfrac{90}{120}=\dfrac{3}{4};\dfrac{15}{25}=\dfrac{3}{5};\dfrac{18}{45}=\dfrac{2}{5};\dfrac{36}{64}=\dfrac{9}{16};\dfrac{32}{72}=\dfrac{4}{9};\dfrac{84}{49}=\dfrac{12}{7}\)

\(\dfrac{3}{4},\dfrac{3}{5},\dfrac{2}{5},\dfrac{9}{16},\dfrac{4}{9},\dfrac{12}{7}\)

a) x = 160

b) x = 5

c) x = 107

d) x = 3

= 36/42=6/7

\(\dfrac{72}{84}=\dfrac{36}{42}\)=\(\dfrac{6}{7}\)

[(6x-72)÷2-84]×28=5628
[(6x-72)÷2-84]      =5628÷28
[(6x-72)÷2-84]      =201
 (6x-72)÷2            =201+84
 (6x-72)÷2            =285
 (6x-72)                =285×2
 (6x-72)                =570
  6x                      =570+72
  6x                      =642
    x                     =642÷26
    x                     =107

[(6x-72):2-84]×28=5628

⇔x=107 .... 

Vậy x=107

\([(6x-72):2-84].28=5628\)

\((6x-72):2-84=5628:28\)

\((6x-72):2-84=201\)

\((6x-72):2=201+84\)

\((6x-72):2=285\)

\(6x-72=285.2\)

\(6x-72=570\)

\(6x=570+72\)

\(6x=642\)

\(x=642:6\)

\(x=107\)

[(6x-72)/3-84]*28=5628

(6x-72)/3-84=5628:28

(6x-72)/3-84=201

(6x-72)/3=201+84

(6x-72)/3=285

6x-72=285*3

6x-72=855

6x=855+72

6x=927

x=927:6

x=154,5

(6x-72):3-84=5628:28

(6x-72):3-84=201

(6x-72):3=201+84

(6x-72):3=285

6x-72=285x3

6x-72=855

6x=855+72

6x=927

x=927:6

x=154,5

( 6x - 84 ) : 2 - 72 = 201

( 6x - 84 ) - 72 = 201 . 2

( 6x - 84 ) - 72 = 402

6x - 84 = 402 - 72

6x - 84 = 330

6x = 330 - 84

6x = 246

x = 246 : 6

x = 41

Vậy x = 41