uses crt;
var a,b,t,i:longint;
begin
clrscr;
   write('a,b= ');readln(a,b);
   //Ting tong cac so le:
   for i:=a to b do if i mod 2=1 then inc(t,i);
   writeln('Tong cac so le: ',t);
   //Toi gian phan so:
   for i:=1 to a do if (a mod i=0)and(b mod i=0) then t:=i;
   writeln(a div t,'/',b div t);
readln
end.

Mã nguồn đây nhé bạn:

program tongSoLe;
uses crt;
var a,b,i,tong,ucln: longint;
begin

clrscr;
write('Nhap a = '); readln(a);
write('Nhap b = '); readln(b);
tong:=0;
for i:=a to b do if i mod 2 = 1 then tong:= tong+i; // neu i la so le, tang tong 1
writeln('Tong cac so le tu ',a,' den ',b,' = ',tong);      // viet ra ket qua
ucln:=a;
repeat                                           // dat ucln la a va giam di 1
ucln:=ucln-1;                                // cho den khi a va b chia het cho ucln
until ( a mod ucln = 0 ) and ( b mod ucln = 0);
writeln('Phan so toi gian cua ',a,'/',b,' la ',a div ucln,'/',b div ucln);
readln;
end.