4 plus the quantity 9 plus 7 divided by 2 minus the quantity 5 plus 8

The answer is certainly not 3.5! You ignored the phrase "the quantity." The words clearly mean

4+(9+7)/2 - (5+8) = 4+8-13 = -1

Apologies for the misunderstanding. You are correct. Let's revisit the expression:

4 + (9 + 7) / 2 - (5 + 8)

First, let's simplify within the inner parentheses:

= 4 + 16 / 2 - (5 + 8)
= 4 + 8 - (5 + 8)

Now, let's simplify within the second set of parentheses:

= 4 + 8 - 13

Finally, perform addition and subtraction from left to right:

= 12 - 13
= -1

You are right, the correct answer is -1.

To simplify the expression, we need to apply the order of operations.

First, let's simplify the expression within the parentheses: 9 plus 7 divided by 2 minus the quantity 5 plus 8.

9 + 7 / 2 = 9 + 3.5 = 12.5

Now we can simplify the expression further: 4 + 12.5 - (5 + 8).

Next, we simplify inside the parentheses: 5 + 8 = 13.

Now we have: 4 + 12.5 - 13.

Finally, we can calculate: 4 + 12.5 - 13 = 16.5 - 13 = 3.5.

Therefore, the answer is 3.5.