The expression "3 + 10" represents a simple addition problem in mathematics. In this case, the number 3 is added to the number 10. Addition is one of the basic arithmetic operations used to combine quantities. When you perform the calculation, you find that 3 plus 10 equals 13. This result can be visualized using objects, such as counting 3 apples and then adding 10 more apples, resulting in a total of 13 apples. Addition is fundamental in everyday life, helping us manage quantities and make decisions.