Find the 100th term of the sequence -7, 3, 13, 23,

-1097
1093
40

First you need to determine which type of sequence is this. Because the difference between 2 successive numbers is constant and it is equal to 10 this sequence is geometric one.

d = 10

To calculate what is the value of some member of this sequence you use formula:

An = Ao + (n-1)*d 
where n represents position of element An, Ao is value of first element in the sequence.
Replacing values we get:
A110 = -7 + 109*10
A110 = 1083.