1设最初明明有X元,天天有Y元,
可列式
0.5X+(Y+0.5X)×1/3-0.5X+(Y+0.5X)×1/3×1/4=675
(Y+0.5X)×2/3+0.5X+(Y+0.5X)×1/3×1/4=1325
X=700
Y=1300