[tex]= [ \frac{40a}{8} -1280*450:15-1990]:2=3805 \\ =[5a-38400-1990]:2=3805 \\ =[5a-40390]:2=3805 \\ = \frac{5a-40390}{2} =3085=\ \textgreater \ 2*3085=5a-40390 \\ 7610=5a-40390 \\ =\ \textgreater \ a= \frac{7610+40390}{5} =\ \textgreater \ a=9600[/tex]
