Question:
A certain store sells only black shoes and brown shoes. In a certain week, the store sold x black shoes and y brown shoes. If 2/3 of all shoes sold that week were black, which of the following expressions represents the value of y, in terms of x?


Solution:

2/3 of all shoes sold were black
=> Out of a total of 3 shoes, 2 were black , and hence, 1 was brown

Since the store sold x black shoes and y brown shoes, we have:

x equivalent to 2 and y equivalent to 1
=> y = x/2

Answer B
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We can create the equation:

x = (2/3)(x + y)

3x = 2(x + y)

3x = 2x + 2y

x = 2y

x/2 = y

Answer: B


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