a, 3/4 ÷ x/6 = 0,75

x/6 = 0,75 ÷ 0,75

x/6 = 1

=> x = 6

Vậy x = 6

b, 2,5 . 45/ x = 5/6

45/x = 5/6  ÷ 2,5

45/x = 1/3

=> x = 45 × 3

=> x = 135

Vậy x = 135

c, x/12 + 121,5 = 121,5

x/12 = 121,5 - 121,5

x/12 = 0

=> x = 0

Vậy x = 0

e, 6/8 = 15/x

3/4 = 15/x

=> x = 20

Vậy x = 20

a,(x-15)-75=0

x-15         =75

x              =75+15

x             =90

b,72-(6.x+5)=55

6.x+5=72-55

6.x+5=17

6.x=17-5

6.x=12

x=12:6

x=2

c,575-(6.x+70)=445

6.x+70=575-445

6.x+70=130

6.x=130-70

6.x=60

x=60:6

x=10

d,(x-34).15=0

x-34=0

x=34

e,15+(18-x)=26

18-x=26-15

18-x=11

x=18-11

x=7

g,(x-5):16=2

x-5=2.16

x-5=32

x=32+5

x=37

45^10*5^20/75^15

=5^10*9^10*5^20/(5^2)^15

=5^10*5^20*9^10/5^30

=9^10

(0.8)^5/(0.4)^6

=(0.4)^5*2^5/(0.4)^6

=2^5/(0.4)

=32/(0.4)

=80

2^15*9^4/6^6*8^3

=2^15*(3^2)^4/2^6*3^6*(2^3)^3

=2^15*3^8/2^6*3^6*2^9

=3^2

=9

a)\(\left(x-18\right)=\frac{75}{25}\)

\(x-18=3\)

\(x=21\)

b) \(\left(27x+6\right):3.11=9\)

\(\left(27x+6\right):3=\frac{9}{11}\)

\(\left(27x+6\right)=\frac{27}{11}\)

\(27x=\frac{27}{11}-6=-\frac{39}{11}\)

\(x=-\frac{39}{11}:27=-\frac{39}{297}=-\frac{13}{99}\)

c) \(\left(15-6x\right).3^5=3^6\)

\(15-6x=3^6:3^5=3\)

\(15-3=6x\)

\(12=6x=>x=2\)

a) \(\left(x-2018\right)\cdot3=0\)

\(\Leftrightarrow x-2018=0\)

\(\Leftrightarrow x=2018\)

b) \(25\left(x-8\right)=0\)

\(\Leftrightarrow x-8=0\)

\(\Leftrightarrow x=8\)

c) \(25+\left(15+x\right)=75\)

\(\Leftrightarrow15+x=50\)

\(\Leftrightarrow x=35\)

a) x=2018

b)x=8

c)x=35

a) 45 -15 = -75 -x

45 -15 + 75 = -x

105 = -x

=> x= -105

Vậy...

a, 45-15=-75-x

=> 30 = -75 - x

=> x = -75 - 30

=> x = -105