A deck of cards contains red cards numbered 1,2,3,4,5,6, blue cards numbered 1,2 and green cards numbered 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21. If a single card is picked at random, what is the probability that the card is red? Give your answer as a fraction.