Need help!! I don't know how to solve these.

What situation is an example of an observational study

6. sarah saved $12.75 every week for a number of weeks, w. she received an additional $25 during the last week in which she saved money. write and solve an equation to find the number of weeks, w, for which sarah had saved money if she has $114.25 now.

Define the type of sequence below. -2,0,2,4,6 a. both arithmetic and geometric b. arithmetic c. neither arithmetic nor geometric d. geometric