Mark has $20 in his bank account. He saves $5 each week. How much money does Mark have in his account after 9 weeks? Use w to represent the number of weeks and t to represent the total amount Mark has after any number of weeks. please explain

Suppose you are analyzing the relationship between time and distance given in a table,and there are 4 values for each quantity.you divide distance 2 minus distance 1 by time 2 minus time 1.you then divide distance 4 minus distance 3 by time 4 minus time 3 and get a different answer.what can you say about the relationship?