Найдите значение выражения: а) 7/15 + 3/10; б) 7/15 - 3/10; в) 5/12 * 9/20; г) 5/12 : 9/20; д) (5/7 + 3 14/18) + 2/7; е) 16 19/40 - (13 + 1 19/40).

а) 7/15 + 3/10 = 14/30 + 9/30 = 23/30.
б) 7/15 - 3/10 = 14/30 - 9/30 = 5/30 = 1/6.
в) 5/12 * 9/20 = 45/240 = 3/16.
г) 5/12 : 9/20 = 5/12 * 20/9 = 100/108 = 25/27.
д) (5/7 + 3 14/18) + 2/7 = (5/7 + 3 7/9) + 2/7 = (5/7 + 2/7) + 3 7/9 = 1 + 3 7/9 = 4 7/9.
е) 16 19/40 - (13 + 1 19/40) = 16 19/40 - 14 19/40 = 2.