mn giúp e với ạ

a: 2+5/6=12/6+5/6=17/6

b: 5/12+3/4+1/3=5/12+9/12+4/12=18/12=3/2

c: 2/3+3/4=8/12+9/12=17/12

\(=>\dfrac{R1}{R2}=\dfrac{l1}{l2}=>\dfrac{20}{R2}=\dfrac{3}{6}=>R2=\dfrac{20.6}{3}=40\Omega\)

a) \(2\left(x+3\right)=4x-\left(2+x\right)\)

\(2x+6=3x-2\)

\(-x=-8\)=>x=8

b) \(\dfrac{1}{x+2}+\dfrac{5}{2-x}=\dfrac{2x-3}{x^2-4}\) đk x khác 2 và -2

\(\dfrac{\left(x-2\right)}{\left(x+2\right)\left(x-2\right)}-\dfrac{5\left(x+2\right)}{\left(x-2\right)\left(x+2\right)}=\dfrac{2x-3}{\left(x-2\right)\left(x+2\right)}\)

=>\(x-2-5x-10=2x-3\)

\(-6x=9=>x=\dfrac{3}{2}tm\)

c) I x-9 I =2x -5

TH1 : x-9 =2x-5 (x≥9)

-x=4=>x=-4 ktm

TH2 9-x=2x-5 (x≤9)

-3x=-14

x=\(\dfrac{14}{3}\) TM

135+(-126)+265+(-164)

=9+101=200

 1b ) đề 
= ( 61 + 41 - 2 ) . 17 
= 100 . 17
=  1700

\(b,\text{PT hoành độ giao điểm: }-2x=3x+3\\ \Leftrightarrow x=-\dfrac{3}{5}\Leftrightarrow y=\dfrac{6}{5}\\ \Leftrightarrow A\left(-\dfrac{3}{5};\dfrac{6}{5}\right)\)

const fi='kt.txt'

fo='kq.out'

var f1,f2:text;

s:string;

i,dem,d:integer;

begin

assign(f1,fi); reset(f1);

assign(f2,fo); rewrite(f2);

readln(f1,s);

d:=length(s);

dem:=0;

for i:=1 to d do 

 if s[i]='e' then inc(dem);

writeln(f2,dem);

close(f1);

close(f2);

end.