the base must be raised
for example
55 = n ( the base is 10 ), then
55 = 
I think its 210 because there are 7 letters and 3 vowels so the permutation would be 7 P 3.
Answer:
4th option (sqrt(10))/2
Step-by-step explanation:

Answer: 25, 31 and 37
Step-by-step explanation:
(2n-1)= 19, 21, 23, 25, 27, 29, 31, 33, 35, 37
(3n+1)= 19, 22, 25, 28, 31, 34, 37,