Bài 5

#Thiet lap string s
s = 'asdvasnvlasvrehwvowvlkxvlkxjvasfoihwefjwflxjlkjfasfihfnlskjflxjfkajsiofhwofyowyfslfj'
print ("Vi tri cuoi cung cua x trong string la: %d" % s.rfind('x'))