<PRE><B>Question 2794</B>
Assume
x = number of balls
y = cost of each ball

x * y = 600
y = 600/x

If each ball costed 0.25$ less, then she would have 10 balls more for the same cost - 
(x+10) * (y-0.25) = 600

This when further simplified comes to
xy + 10y - 0.25x - 2.5 = 600
600 + 10y - x/4 - 2.5 = 600
10y -x/4 = 2.5

Multiplying this whole equation by 4
40y - x = 10
40 (600/x) - x = 10

Multiplying the whole equation by x
24000 - x2 = 10x
x2+10x=24000

So x =150 and hence y = 600/150 = 4

So the store owner bought 150 balls for 4$ each</PRE>