GMAT Quantitative Reasoning Practice Test 8

We are told that the stock increases its value by a constant rate and therefore we need to find some kind of pattern in order to know the value every year.
Statements (1) and (2) taken together are sufficient since they give us the percent increase of the stock from 1991 to 1992, which is 15%. The value of the stock in 1998 can be easily calculated, add 15% every year until 1998.