Marcus and his brother always argue about who will walk the dog the father wants to find a random way of deciding who will do the job he invented a game to help them decide. Each boy will have a bag with three colored blocks in it one yellow, one green, and one white. Each night before dinner, each boy draws a block out of his bag. If the colors match, Marcus walks the dog. It's a true colors do not match, his brother walks the dog Marcus's father wants to be sure that the game is fair make a probability tree of all the possible combinations of draws that Marcus and his brother could make. How many possibilities are there?