You always perform multiple/divide before you do plus/minus, just like you would do powers. It's how mathematics is done.
Brackets would only be needed if you wanted to change that order.
2x18+1 = 36+1 = 37
If you wanted to add 1 first, you must use brackets. ie 2x(18+1)
@Ark: He could be pointing, but he still wasn't finished.