Gọi 2 số cần tìm là a và b; theo bài ra ta có:

\(a+b=162=>4a+4b=648\) ;

\(\dfrac{1}{4}a+12=\dfrac{1}{3}b=>12\left(\dfrac{1}{4}a+12\right)=12\left(\dfrac{1}{3}b\right)\)

\(=>3a+144=4b\) ; thay vào trên ta có:

\(4a+3a+144=648\)

\(=>7a=504=>a=72\) ; \(=>b=162-72=90\)

Vậy hai số cần tìm là 72 và 90;

CHÚC BAN HỌC TỐT.................

a) 2.3^x =162

3^x =162:2

3^x=81

3^x=3⁴

vậy x bằng 4

ban co the lam cau b) , c) khong

81:3^x=3

=> 3^x =81:3

=>3^x=27

=> x=3

3^x+1.2=162

=> 3^x+1=162:2

=> 3^x+1= 81

=> x+1=4

x=3

\(81:3^x=3\)

\(3^x=27\)

\(3^x=3^3\)

\(\Rightarrow x=3\)

Trả lời:

\(a,3^{x-1}+5.3^{x-1}=162\)

\(\Rightarrow3^{x-1}.\left(1+5\right)=162\)

\(\Rightarrow3^{x-1}.6=162\)

\(\Rightarrow3^{x-1}=27\)

\(\Rightarrow3^{x-1}=3^3\)

\(\Rightarrow x-1=3\)

\(\Rightarrow x=4\)

Vậy x = 4

\(b,2^{x+5}+2^{x+2}=576\)

\(\Leftrightarrow2^{\left(x+2\right)+3}+2^{x+2}=576\)

\(\Rightarrow2^{x+2}.\left(2^3+1\right)=576\)

\(\Rightarrow2^{x+2}.9=576\)

\(\Rightarrow2^{x+2}=64\)

\(\Rightarrow2^{x+2}=2^6\)

\(\Rightarrow x+2=6\)

\(\Rightarrow x=4\)

Vậy x = 4

c, x = 6

a) \(\left(\frac{-1}{6}+\frac{5}{-12}\right)+\frac{7}{12}=\left(\frac{-2}{12}+\frac{-5}{12}\right)+\frac{7}{12}=\left(\frac{-7}{12}\right)+\frac{7}{12}=0\)

b)\(\frac{7}{36}-\frac{8}{-9}+\frac{-2}{3}=\frac{7}{36}+\frac{32}{36}-\frac{24}{36}=\frac{15}{36}=\frac{5}{12}\)

c) \(\frac{3}{5}-\frac{2}{5}.\frac{10}{12}=\frac{3}{5}-\frac{2}{5}.\frac{5}{6}=\frac{3}{5}-\frac{1}{3}=\frac{9}{15}-\frac{5}{15}=\frac{4}{15}\)

d) \(\frac{2}{\left(-3\right)^2}+\frac{5}{-13}-\frac{-3}{4}=\frac{2}{9}-\frac{5}{13}+\frac{3}{4}=\frac{8}{36}-\frac{15}{36}+\frac{27}{36}=\frac{5}{9}\)

mình giải ý c 

5(x+27)=200

(x+27)=200:5

(x+27)=40

x=40-27

x=13