已知a/3=b/4=z/5 且2a-b+c=18 求a+2b-c

已知a/3=b/4=z/5 且2a-b+c=18 求a+2b-c
已知a/3=b/4=z/5 且2a-b+c=18 求a+2b-c

已知a/3=b/4=z/5 且2a-b+c=18 求a+2b-c
因为 a/3 = b/4 = c/5
所以设 a = 3k ,b = 4k ,c = 5k
因为 2a - b + c = 18
所以 6k - 4k + 5k = 18
k = 18/7
a + 2b - c
= 3k + 8k - 5k
= 6k
= 6×(18/7)
= 108/7