Final answer:
The teacher can make 21 completed sets of 4 pens.
Step-by-step explanation:
To find the number of completed sets the teacher can make, we need to divide the total number of pens by the number of pens in each set. In this case, the teacher has 86 pens and wants to group them into sets of 4. To find the number of completed sets, we divide 86 by 4: 86 ÷ 4 = 21 with a remainder of 2. So the teacher can make 21 completed sets of 4 pens.
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