7 11/15-(3 9/20+1 целых1/30)=
= 116/15 - (69/20 - 31/30) = 116/15 - (207+62)/60 = 116/15 - 269/60 = (464 - 269)/60 = 195/60 = 3,25
7 11/15-(3 9/20+1 целых1/30)= 116/15 - (69/20 - 31/30) = 116/15 - 269/60 = 195/60 = 3,25