Ok, just in case you are completely new to C-style programming...
The characters "//" begin what is called a
comment, more specifically an inline comment. Everything from the // all the way to the end of the line is
completely ignored by the compiler. It's a way for you to make notes in your code.
As to the question, I must say it makes no sense.
• Calculate a_y where a_y = -9.8m/s^2
How can you "calculate" something that's just a definition? This is like saying "calculate A where A = 1". I think there is something missing here.