Order of operations is and order that you go by addition, subtraction, multiplication, division, exponentiation, and grouping.
Usually its just the first four because that's usually what you get in home work or assignments. If there is no addition you skip to multiplication and so forth. And the equation in parentheses usually goes first before you solve anything else. .
For example in your first question you would do addition first then subtraction. Since there is no multiplication or division you don't have to include that. 34 + 17 = 51 - 5 = 46