18/ а+23=3/5 4/7=8+2а/ 21 5/12=30/ 44+7а 1/9=5а-14/ 54 3/8=21/ 4(a+8) 14/45=7(a-5)/ 90

18/(а+23)=3/5      4/7=(8+2а)/21     5/12=30/(44+7а)     1/9=(5а-14)/54
а+23=18:3/5        8+2а=21*4/7       44+7а=30:5/12       5а-14=54*1/9
а+23=30              8+2а=12            44+7а=72               5а-14=6
а=30-23               2а=12-8             7а=72-44                5а=6+14
а=7                     2а=4                  7а=28                    5а=20
                          а=2                     а=4                       а=4

3/8=21/(4(а+8))        14/45=(7(а-5))/90
4а+32=21:3/8           7а-35=90*14/45
4а+32=56                7а-35=28
4а=56-32                  7а=28+35
4а=24                      7а=63
а=6                          а=9