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解法如下:
设0.6元的邮票有x张,则0.8元的邮票有(25-x)张
0.6x+0.8(25-x)=18.4
0.6x+20-0.8x=18.4
-0.2x =-1.6
x =8
则0.8元的邮票有25-x=25-8=17(张)
答:0.6元的邮票有8张,0.8元的邮票有17张