We replace each occurrence of z with the number 4, and simplify

(1 + z) × 2 + 12 ÷ 3 - z

It is not clear what is being divided by the last terms.

To replace each occurrence of z with the number 4, you simply substitute z with 4 in the expression:

(1 + 4) × 2 + 12 ÷ 3 - 4 = 5 × 2 + 12 ÷ 3 - 4

Now let's simplify the expression by following the order of operations (also known as PEMDAS or BODMAS):

Step 1: Perform multiplication and division from left to right
5 × 2 = 10
12 ÷ 3 = 4

So the expression becomes:

10 + 4 - 4

Step 2: Perform addition and subtraction from left to right
10 + 4 = 14
14 - 4 = 10

Therefore, the simplified expression is 10.