Gerald likes peppers, he planted a whole garden full of peppers... He had green, red, yellow colored peppers. In the first row of his garden he had 12 red, 15 green, and 5 yellow pepper plants. In the second row of his garden he had 6 red, 12 green, and some yellow pepper plants. If he had a total of 18 red pepper plants, 20 yellow pepper plants, How many total pepper plants did he have in his garden?