23 + 5 × 10 ÷ 2 – 33 + (11 – 8)

Answer 1

Use PEMDAS.

http://www.mathsisfun.com/operation-order-pemdas.html

Answer 2

23 + 5 × 10 ÷ 2 – 33 + (11 – 8)
23 + 5 × 10 ÷ 2 – 33 + 3
23 + 50 ÷ 2 - 33 + 3
23 + 25 - 33 + 3
48 - 33 + 3
15 + 3
18