5.445 Вычислите: a) 1/2 + 1/3; б) 1/3 + 2/7; в) 2/5 + 1/3; г) 3/7 + 4/9; д) 5/9 - 1/6; е) 3/4 - 1/3; ж) 1/6 + 1/3; з) 9/5 - 7/10; и) 1/2 - 3/8; к) 7/15 - 3/10; л) 3/8 + 5/12; м) 5/9 - 1/6; о) 17/30 - 3/6; п) 17/35 - 4/15.

• a) 1/2 + 1/3 = 3/6 + 2/6 = 5/6
• б) 1/3 + 2/7 = 7/21 + 6/21 = 13/21
• в) 2/5 + 1/3 = 6/15 + 5/15 = 11/15
• г) 3/7 + 4/9 = 27/63 + 28/63 = 55/63
• д) 5/9 - 1/6 = 10/18 - 3/18 = 7/18
• е) 3/4 - 1/3 = 9/12 - 4/12 = 5/12
• ж) 1/6 + 1/3 = 1/6 + 2/6 = 3/6 = 1/2
• з) 9/5 - 7/10 = 18/10 - 7/10 = 11/10
• и) 1/2 - 3/8 = 4/8 - 3/8 = 1/8
• к) 7/15 - 3/10 = 14/30 - 9/30 = 5/30 = 1/6
• л) 3/8 + 5/12 = 9/24 + 10/24 = 19/24
• м) 5/9 - 1/6 = 10/18 - 3/18 = 7/18
• о) 17/30 - 3/6 = 17/30 - 15/30 = 2/30 = 1/15
• п) 17/35 - 4/15 = 51/105 - 28/105 = 23/105

Ответ: a) 5/6; б) 13/21; в) 11/15; г) 55/63; д) 7/18; е) 5/12; ж) 1/2; з) 11/10; и) 1/8; к) 1/6; л) 19/24; м) 7/18; о) 1/15; п) 23/105.