In this case, you have to multiply the price of the one way journey ($2.65) by 8 (as this is the number of individual journeys made in one week. It's gives you $21.20. As he has 1 bottle of water at $1.45 each day for four days, you have to multiply these together, giving you $5.80
You then have to add together $21.20 and $5.80, giving you $27.
Therefore, it costs Edgar $27 a week