miuCH4 = 16 g/mol
miuC2H6 = 30 g/mol
miuC3H8 = 44 g/mol
avem a moli CH4, b moli C2H6 si c moli C3H8
=> 16a + 30b + 44c = 416
a/1 = b/2 = c/3 => b = 2a, c = 3a
=> 16a + 30x2a + 44x3a = 416
=> a = 2 moli CH4
=> b = 2a = 4 moli C2H6
=> c = 3a = 6 moli C3H8
cred ca de aici te descurici cu calculele.... pentru cele doua cerinte...??!!