2 1/4 + 1 2/4 ≠ 5
Why?
2 1/4 + 1 2/4
=3 3/4
The answer is wrong because the student added wrong. The real answer is 3 3/4.
the diamiter is the two out side numbers minused by 3.14
since the lengths of all those four sides are in a 3:2:6:7 ratio, and the whole perimeter is 126, what we do is, simply divide the whole by (3+2+6+7) and distribute accordingly.

Odd + odd = even + odd = odd
adding 3 odd numbers would make an odd answer