Выполните действие помогите плиз
a) 3/11 + 5/22 = 6/22 + 5/22 = 11/22 = 1/2
б) 11/12 - 7/15 =55/60 - 28/60 = 27/60 = 9/20
в) 11/15 - 3/20 + 1/30 = 44/60 - 9/60 + 2/60 = 37/60