105÷3+4-{4+[13+5×(8-5×a)]÷4}=28

Răspuns :

35+4-{4+[13+5x(8-5xa)]:4}=28
39-28=4+[13+5x(8-5a)]:4
(11-4)x4=13+5x(8-5a)
7x4=13+5x(8-5a)
28-13=40-25a
25a=40-15
25a=25
A=1