Again, those aren't questions. I can think of three different interpretations for the first line.

1. You might mean the amount of time it takes for a TLB hit to occur, and the amount of time for a cache hit to occur... but that's already given as 4ns and 10ns, so why would anyone ask?
2. You might want to find the expected access time presuming a TLB hit followed by a page table hit, with the next step being unknown but following the ratios given.
3. You might want to find the probability that you have a TLB hit followed by a cache hit.

I dunno. Perhaps I'm just stressed, but if you can't be bothered to write a clear question, I can't be bothered to answer it....


As a general example, though, suppose you have a cache and storage. You hit the cache 1 time in 3 for whatever data you're accessing. The cache takes 5ns, storage takes 15ns. What's the expected data recovery time overall?

1/3rd of the time it's 5ns; (1-1/3rd) = 2/3rds it's 15 ns. So, overall this is just 5ns/3 + 2*15ns/3 = 35/3 ns ~= 11.67 ns.

Perhaps that will help you....