解(1)：当销售单价为x元(x﹥100)时,销售单价增加了(x-100)元,年销售量减少了[(x-100)/10]万件,实际销售量为{20-[(x-100)/10]}万件,因此,有：
y=20-[(x-100)/10]
=20-(x/10)+10
=30-(x/10)
=-(x/10)+30
y=-(x/10)+30
(2)：当销售单价为x元时,每件销售利润为(x-60)元,销售量为[-(x/10)+30]万件,有：
z=(x-60)[-(x/10)+30]
=-(x²/10)+30x+6x-1800
=-(x²/10)+36x-1800
z=-(x²/10)+36x-1800
(3)：z=-(x²/10)+36x-1800
=(-1/10)(x²-360x)-1800
=(-1/10)(x²-360x+180²)-1800+180²×1/10
=(-1/10)(x-180)²+1440
当x=180时,年利润z有最大值,最大年利润是1440万元.