[問題] PP2-DS-109
這題感覺上答案應該是Ｃ，不過詳解上的答案是Ｂ，我看不懂詳解上的思路，有好心
人可以指點一下嗎？
謝謝。
109.
Marta bought several pencils. If each pencil was either a 23-cent pencil or
a 21-cent pencil, how many 23-cent pencils did Marta buy?
(1) Marta bought a total of 6 pencils.
(2) The total value of the pencils Marta bought was 130 cents.
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【答案】B
【思路】
(2) 2x+ 21(x+y) = 130
x+y =6
x=2, y=4……sufficient
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