Respuesta :

texaschic101
(12 - 9) / 12 = (40 - x) / 40
3/12 = (40 - x) / 40
40(1/4) = 40 - x
10 = 40 - x
10 - 40 = -x
-30 = -x
30 = x <=== percent decrease from 40 to 30