I believe it is 1/2x+7 because multiplying anything by 1/2 gives you half of that number in this case being x. And adding seven would give you 7 more than half of x.
If x represents a number, Then an equation where 7 is more than half the number would be 1/2x>7 or 1/2x+7. It depends on if the question is dealing with inequalities or not.
