Во 2 просто надо дописать 1 строчку
var a,b,c,m,s:integer;
begin
read(a);
b:=a mod 10;
c:=a div 10;
m:=c mod 10;
c:=c div 10;
s:=b+c+m;
write(s);
end.
3) var a:integer;
begin
read(a);
if (a mod 5=0) and (a mod 10 <>0) and (a mod 7=0) then
write('YES') else write('NO');
end.