1) 18 3
-------- = -----
а + 23 5
3 * (а + 23) = 18 * 5
3а + 69 = 90
3а = 90 - 69
3а = 21
а = 21 : 3
а = 7
2) 4/7 = 8+2а / 21
7 * (8 + 2а) = 4 * 21
56 + 14а = 84
14а = 84 - 56
14а = 28
а = 28 : 14
а = 2
3) 5/12 = 30 / 44+7а
5 * (44 + 7а) = 12 * 30
220 + 35а = 360
35а = 360 - 220
35а = 140
а = 140 : 35
а = 4
4) 1/9 = 5а-14 / 54
9 * (5а - 14) = 1 * 54
45а - 126 = 54
45а = 54 + 126
45а = 180
а = 180 : 45
а = 4
5) 3/8 = 21 / 4*(а+8)
3/8 = 21 / 4а + 32
3 * (4а + 32) = 21 * 8
12а + 96 = 168
12а = 168 - 96
12а = 72
а = 72 : 12
а = 6
6) 14/45 = 7*(а-5) / 90
14/45 = 7а-35 / 90
45 * (7а - 35) = 90 * 14
315а - 1575 = 1260
315а = 1260 + 1575
315а = 2835
а = 2835 : 315
а = 9