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40 + 60 ( 1500 - x ) = 80000
100 ( 1500 - x ) = 80000
100 ( 1500 - x ) * 100 = 80000 * 100
1500 - x = 800
1500 - x + x = 800 + x
1500 = 800 + x
1500 - 800 = 800 + x -800
700 = x
x = 700

2006-11-22 21:18:46 補充：
送埋 checking 比你 !!呢個係我學校寫法 !!Checking : sub. x = 700 into the eqt.L.H.S = 40 + 60 ( 1500 - x )=100 ( 1500 - 700 )=100 ( 800 )= 80000= R.H.S

2006-11-22 21:20:41 補充：
Checking 留左最後個句 !!Checking : sub. x = 700 into the eqt.L.H.S = 40 + 60 ( 1500 - x )=100 ( 1500 - 700 )=100 ( 800 )= 80000= R.H.S∴ x = 700 is the solution of the eqt.

40+90000-60x=80000
-60x=80000-40-90000
-60x=-10040
60x=10040
x=10040/60
x=502/3

40+90000-60x=80000
10040=60x
1004=6x
x=502/3