To answer this question, use permutation since the order of the letter matters. There are 7 letters and only 4 are to be used for the code. This is a permutation of 7 taken 4 (7P4) which is equal to 840. Thus, the sample space is 840.
For the next questions, there are 3 vowels for as the first letter, only 6 letters are available for the second, 5 on the next, and 4 on the last. Multiplying these numbers give 360. To solve for probability, divide this number with the sample space. Thus, the answer is 3/7.
Answer:
I'm not 100% sure on this but I think it would be C- 8.1
Step-by-step explanation:
what is your clear question? it lacks some details
Answer:

Step-by-step explanation:
Given

Required:
Simplify
We start by opening the bracket


Collect Like Terms

Hence, the equivalent expression is 
Answer:
It decreased
Step-by-step explanation:
It decreased. Assuming that the temperature is 100 and it is now reduced by 60% then the temperature will be at 40 and if it increased by 80% then the final temp is 72. So it is 48% of the original temp.