x：y：z=3:4:7
令x=3a y=4a z=7a
2x-3y+z=18
6a-12a+7a=18
a=18
3x-2y+z
=9a-8a+7a
=8a
=8×18
=144
x：y：z=3:4:7 2x-3y+z=18 求：3x-2y+z
3个回答
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