Amy's sells kale at x dollar per pound for the first 20 pounds and 0.8x for every subsequent pound. Lucia's price is x per pound for the first 14 pounds and 0.9x for subsequent pounds. What is the minimum number of pounds over 15 for which Amy's becomes an equal or better deal?

A. 24
B. 25
C. 26
D. 27
E. 28


Are You Up For the Challenge: 700 Level Questions
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Amy’s price — 20x+ 0.8x*a
Lucy’s price — 14x + 0.9x*b
—> 20x+ 0.8x*a ≥ 14x+ 0.9x*b

Let’s find the minimum number of (20 + a ) :

20x + 0.8x*a = 14x + 0.9x*b
6x = x( 0.9b —0.8a)
—> \(a = \frac{(9b —60)}{8} \)— must be integer

If \(b= 12\) , then \( a = \frac{(108–60)}{8 }= 6 \)
—> \(20 + a = 26\)

The answer is C

Posted from my mobile device

The question is confusing on two counts:
The first, as explained by IanStewart, is that it can be logically interpreted to mean the solver has to find the minimum number of pounds that a buyer has to buy IN EXCESS OF 15 POUNDS so that he gets an equal or better deal from Amy than from Lucia.
The second is the condition in the stem which states that "Amy's becomes an equal OR better deal". According to this, the correct answer could be either C (26 lbs) (the buyer spends the same amount of money whether he buys from Amy or Lucia) or D (27 lbs) ( where he spends less money when he buys from Amy).

Corrigendum: Sorry, my second point is incorrect - I overlooked the "minimum number of pounds" stipulation. First point stands though.