What is the result of adding 5 + 15?

The result of adding 5 and 15 is 20. This is determined by simply combining the two numbers together. When you add them, you can visually or mentally count up from 5 by 15 units. Starting at 5 and counting up, you first reach 10 (which is 5 + 5) and then continue to 15 (5 + 10), and finally arrive at 20 (5 + 15).

This arithmetic operation illustrates a basic principle of addition where the sum is the total amount after combining multiple quantities. Thus, 5 + 15 equals 20, which is why this option is the correct answer.