I have three responses from my consultants for you.
Use the same idea as the "half of 11" but first write 12 another way (using another numbering system).
Stephen La Rocque.>
Teacher's answer is probably to use Roman Numerals. But I agree with you! Let's do mathematics in math classes. Save the party games for recess.
Well there are ways but maybe a bit far out for a grade 8 student.
Normally, that is in base ten, when we write 12 we mean 1x10 + 2x1; the first column on the right is the units column and the second column is the tens column. Thus 25 means 2x10 + 5x1, etc.
There is nothing special about base ten, in fact computers use base two. If we were to use base twelve, then, in base twelve, 12 means 1x12 + 2x1 = fourteen and half of fourteen is indeed seven.
I'm sure there are other ways to solve the problem also.