quá dễ
uses crt;
var a,b,c:integer;
begin
clrscr;
write('a='); readln(a);
write('b='); readln(b);
write('c='); readln(c);
if (a<0) and (a mod 3=0) then writeln(a,' thoa man dieu kien')
else writeln(a,' khong thoa man dieu kien');
if (b<0) and (b mod 3=0) then writeln(b,' thoa man dieu kien')
else writeln(b,' khong thoa man dieu kien');
if (c<0) and (c mod 3=0) then writeln(c,' thoa man dieu kien')
else writeln(c,' khong thoa man dieu kien');
readln;
end.