Jason is playing a game. He has two sets of cards. One set has three red cards, numbered 1, 2 and 3. The other set has four green cards, numbered 4, 5, 6 and 8. Jason chooses a red card and a green card at random. He works out his score by adding the numbers on the two cards together. A sample space diagram is drawn below. Work out the probability that Jason gets a score of 9 or more.