Leah wrote 4 letters and correctly addressed 4 envelopes. She put one letter into each envelope, but she was careless and got some of them mixed up. As it happened, one of these three things was how it came out: she got exactly 3 of them right, or she got exactly 2 of them right, or she got exactly one of them wrong. How many did she get right?
She got 2 of them right. (3 right is the same as 1 wrong, and 1 wrong is impossible.)