Hi Thomas,
Check out the exponent rules if you can, i'm not too clear on what the first part of your question is (a)^{8}? You may need to provide some more information on that
But your second question is all about exponential rules. Remember x^{3} is the same as (x*x*x)
so (x^{3})^{2} can be written as (x*x*x)(x*x*x) which is x^{6 }, know that if a function has an exponent on the outside of the parenthesis you can multiply it, to save time, (x^{3})^{2} , 3*2= 6, so x^{6}
Looking at your problem, it can written as (4y^{3})(4y^{3}) which would be equal to
16y^{6}
You should definitely check out exponent rules if you can, to clear up any confusion.
Hope this helps you!