Final answer:
John is engaging in the process of summation, which is the act of adding a sequence of numbers to find their total sum.
Step-by-step explanation:
When John takes several variables and adds them together, he is engaging in the process called summation. Summation is defined as the operation of adding a sequence of numbers; the result is their sum or total. This concept is often utilized in mathematics to simplify complex equations or scenarios where multiple values contribute to a final result. For example, when calculating the total time to complete parallel tasks or the addition of vectors, the summation process is crucial for reaching a comprehensive conclusion.