Phillipa rode her bicycle every day over the weekend. Phillipa rode [ ( 13 . 5 + 8 . 5 ) ÷ 2 ] miles on Friday, [ 18 − ( 2 × 4 ) ] miles on Saturday and [ 20 − ( 5 − 3 ) ] miles on Sunday. On which day did Phillipa ride her bicycle the most? She rode her bicycle the most on .