Amybrettand cate secretly write down ZUor T. What is the probability that Cate's letter is different from both Amy's letter and Brett's letter?

The total number of possible outcomes is 2 (Z or T). For Cate's letter to be different from both Amy's and Brett's, there are 2 possibilities out of 2 for Cate. Therefore, the probability is 2/2, which simplifies to 1. So, the probability that Cate's letter is different from both Amy's and Brett's is 1 or 100%.