First you must distribute the 3 to the numbers inside the parentheses, which would be x and -1...
5 + (3*x) + (3 * (-1) )
5 + 3x + (-3)
5 + 3x - 3
Now you must combine like terms. Like terms are numbers that have matching variables OR are numbers with out variables. In this case the like terms are 5 and -3, since they both don't have any variables attached.