Answer:
8421
Step-by-step explanation:
8050 < abcd < 8500
We must have a = 8, so the number is 8bcd.
The value of a is 20 times the value of b, or a= 2b.
a = 8, so b = 4.
The value of b is 20 times the value of c, or b = 2c.
b = 4, so c = 2.
The value of c is 20 times the value of d, or c = 2d.
c = 2, so d = 1.
The secret number is 8421.
If the number is big enough there can be up to an infinite number of decimals
Answer:
No solutions
Step-by-step explanation:

Substitute 3^x with t and we get.

Answer:
combination
Step-by-step explanation:
permutation is when there is a specific order, whereas combination is when they are not in any specific pattern (in this case, 5/13 students, not in any particular order. just 5.
I don't want to explain circular permutation right now (it's difficult to explain), but it's not it from my knowledge