this helpful calculator, which will do the work for you.
You should find that the sum of the three prime factors is 100. So how many ways can 100 be the sum of three primes? Answer: not many, because the sum of three odd numbers is odd, so one of the three primes will always have to be the only even prime, namely 2. To complete the question, you just have to work out how many ways there are to write 98 as a sum of two (odd) primes.