Quote:
Originally Posted by Mr. Hui
You can do 144/4 or 4b first. The order does not change the answer.

I think this a case where a pair of parentheses can clear up a lot of confusion.
Mr. Hui is assuming that the above expression, as written, is equivalent to:
12^2 / (4b) + 4 so that when b = 9 the answer is 4. When he says it doesn't matter what order you evaluate 144/4 or 4b first he is assuming you would get either 144/4/9, or 144/36 which are the same.
However, others are assuming that the expression is equivalent to:
(12^2 / 4) x b + 4 which evaluates to 328.
As the expression is originally written I believe it has to be evaluated the second way so that the answer is 328.
12^2 / 4b + 4
144 / 4b + 4 Evaluate exponents
36 x b + 4 Evaluate division left to right
36 x 9 + 4 Substitution
324 + 4 Multiplication
328 Addition
The 4b term is what is confusing as we are used to treating it as a term in itself so that it seems like we have 144 / 36 when b = 9.