Final answer:
The teacher can write 495 different tests by choosing 4 questions out of 12 using the combination formula.
Step-by-step explanation:
To calculate the number of different tests the teacher can write, we need to use the combination formula. The combination formula is given by C(n, r) = n! / ((n - r)! * r!), where n is the total number of questions and r is the number of questions to choose. In this case, n = 12 and r = 4. Substituting the values into the formula, we have C(12, 4) = 12! / ((12 - 4)! * 4!). Evaluating this expression, we find that there are 495 different tests the teacher can write.
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