Question

太好玩了o(^▽^)o

不好意思請問這題怎麼解？

) 2.若a:b:c4:5:6,且4a+56-6c=15,則a+b-c=?
(A) 3 (B) 9 (C) 15 (D) 21

Answer 1

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a : b : c = 4 : 5 : 6 = 4k : 5k : 6k

4*4k + 5*5k - 6*6k = 15
5k = 15
k = 3

=> a = 12, b = 15, c = 18

a + b - c = 12 + 15 - 18 = 9