I am having a lot of problems with this problem, I went to a tutor and showed me what to do, but I still get it wrong. Im on the verge of failing, so i want to get the best possible grades on my homework. Please help me with this problem:

If a die is rolled 40 times, there are 640 different sequences possible. What fraction of these sequences have exactly 8 numbers less than or equal to 3? (Round your answer to the nearest 0.0001.)