643=4x160+n =that is the problem
n=3
Answer: The 9th term is 6561
Step-by-step explanation:
The geometric sequences have the following formula

Where
is the first term of the sequence and r is the common ratio between the consecutive terms of the sequence
In this case the sequence is 1 -3 9 -27
So 
Observe that the common ratio r is:

So the formula is:

We want to find 


Answer:
$4 Change
Step-by-step explanation:
18 x 2 = 36
15 x 4 = 60
100 - 36 - 60 = 4