Use the order of operations to simplify the expression: 23 + 5 × 10 ÷ 2 – 33 + (11 – 8)

Here you must do mult. and div. BEFORE add'n. and subtr'n.

23 + 5 × 10 ÷ 2 – 33 + (11 – 8)
Mult 5*10, and then div. the result by 2.  Then you will have

23 + 25 - 33 + 3
This simplifies to:  51-33 =   18

Use PEMDAS. (Multiplication & divison + addition & subtraction are not in order, solve it from left to right)
Parentheses
Exponents
Multiplication
Division
Addition 
Subtraction

23 + 5 × 10 ÷ 2 - 33 + (11 - 8) 
Do the parentheses first. 

23 + 5 × 10 ÷ 2 - 33 + (3)
Now do multiplication since its first when you read the problem from left to right.

23 + 50 ÷ 2 - 33 + 3
Use division.

23 + 25 - 33 + 3
Now you can solve from left to right.

48 - 33 + 3
15 + 3
18

Using the order of operations, the expression can be simplified to 18.