503.
а) 3/16 + 5/8 = 3·1/16·1 + 5·2/8·2 = 3/16 + 10/16 = 3 + 1016 = 1316
б)11/16 + 3/8 = 11·1/16·1 + 3·2/8·2 = 11/16 + 6/16 = 11 + 6/16 = 17/16 = 1 + 1·1616 = 11/16( одна целая одна 16)
в)11/18 + 1/6 = 11·1/18·1 + 1·3/6·3 = 11/18 + 3/18 = 11 + 3/18 = 14/18 = 7·2/9·2 = 7/9
г)1/18 + 5/6 = 1·1/18·1 + 5·3/6·3 = 1/18 + 15/18 = 1 + 15/18 = 16/18 = 8·2/9·2 = 8/9
504
a)4/5 + 2/15 = 4·3/5·3 + 2·1/15·1 = 12/15 + 2/15 = 12 + 2/15 = 14/15
б)1/2 + 3/8 = 1·4/2·4 + 3·1/8·1 = 4/8 + 3/8 = 4 + 3/8 = 7/8
в)4/21 + 2/7 = 4·1/21·1 + 2·3/7·3 = 4/21 + 6/21 = 4 + 6/21 = 10/21
г)1/24 + 5/6 = 1·1/24·1 + 5·4/6·4 = 1/24 + 20/24 = 1 + 20/24 = 21/24 = 7·3/8·3 = 7/8