How do you find the rule given a sequence of numbers?

It depends on the sequence type.

if it's a regular sequence with a first common difference, you can use the formula a+d(n-1). here, "a" is the first term, "d" is the common difference and "n" is the term number.

Idon’t know actually i’m in 5th grade and don’t know

That is so true, i can’t believe how true this is