Colin thought that he got 12 questions wrong, but he actually got 5 of those questions right. This means that he actually got 7 questions wrong that he thought he got wrong.
Since he got a total score of 42 out of 50, this means that he got 8 questions wrong that he thought he got right.
Therefore, Colin predicted that he got (50 - 12) = 38 questions right, but he actually got (50 - 8 - 7) = 35 questions right.
To find the percentage accuracy of Colin's predictions, we can use the formula:
percentage accuracy = (number of correct predictions / total number of predictions) x 100%
In this case, the number of correct predictions is 35 out of 50, since Colin got 35 questions right out of the 50 total questions. The total number of predictions is 38, since Colin predicted that he got 38 questions right.
Using the formula, we get:
percentage accuracy = (35 / 38) x 100% = 92.11%
Therefore, Colin had a prediction accuracy of 92.11%.