幾條數學題

(-9.7)-〔(+2.4)-(-8)〕
=(-9.7)-(2.4+8)
=(-9.7)-(2.4+8)
=(-9.7)-(10.4)
=-20.1

(+11)-(-2)〔(+6)(-3)+(-2)〕
=(11)-(-2)(-18-2)
=(11)-(-2)(-18-2)
=(11)-(-2)(-20)
=11-40
=-30

〔(-5)(-2)-(+3)〕〔(-6)+(-4)〕(+2)
=(10-3)(-10)(2)
=(7)(-20)
=-140

原來的錢=3200除(1-20%)
=3200除0.8
=$4000

(-9.7)-〔(+2.4)-(-8)〕
(-9.7)-(2.4+8)
(-9.7)-10.4
= -20.1


(+11)-(-2) 〔(+6)(-3)+(-2)〕
(11+2) (6-3-2)
13(1)
= 13


〔(-5)(-2)-(+3)〕〔(-6)+(-4)〕(+2)
(-5-2-3) (-6-4) (2)
(-10) (-10) (2)
=200

用去一筆錢的20%後，餘下$3200。求原來的錢。
3200/(1-20%) = $4000 "/" 除號

2010-01-03 13:14:52 補充：
第2條也看錯
(+11)- (-2)〔(+6)(-3)+(-2)〕
11+ (2) (-18-2)
(11) (40)
440

第3條看錯=.=
〔(-5)(-2)-(+3)〕〔(-6)+(-4)〕(+2)
((-10)-3) (-6-4) (2)
(-13) (-10) (2)
=260