The expression "2 + 7" represents a simple addition problem in mathematics. In this case, the number 2 is combined with the number 7 to find the total. Addition is one of the basic operations in arithmetic, which is a branch of mathematics dealing with numbers and their relationships. When you add 2 and 7, you count up from 2 by 7 more units. This results in a total of 9. Therefore, the solution to the equation "2 + 7" is 9, which can also be visualized using objects, such as counting 2 apples and then adding 7 more apples to get a total of 9 apples.