Final answer:
The domain of the expression x + 7 + 5 is all real numbers, as there are no restrictions on the values that x can take in this linear expression.
Step-by-step explanation:
The domain of an expression or function is the set of all possible values that x can take for which the expression is defined. For the expression x + 7 + 5, there are no restrictions on the value of x because it is simply a linear expression that does not involve division by zero or square roots of negative numbers, which are the usual restrictions on the domain in algebra. Therefore, the domain of x + 7 + 5 is all real numbers.