A. Used to keep track of very large and very small numbers during mathematical calculations.
Step-by-step explanation:
Some very large and small numbers are not easily represented in mathematical calculations. Using scientific notations help us to represent very large and small numbers to the power of 10.
I'd say what you would do is:
You can either
1. Add 15 and 18 together and then divide by 2
OR
2. Since there is a 3 number difference between 15 an 18, just add 3 to 18
