SOLUTION: Hi 4000 towels are for sale.the ratio of blue to red was 2:1.the rest were white. After 1/4 of the blue towels and half of the white were sold, there were 2400 towels left. How ma

Let x be the number of red towels initially.

Then the number of blue towels initially is 2x, according to the condition.

Let w be the number of white towels initially.


Then you have these two equations in 2 unknowns:

2x + x + w = 4000       (1)    ("4000 towels are for sale.the ratio of blue to red was 2:1.the rest were white.")

 = 2400   (2)    ("After 1/4 of the blue towels and half of the white were sold, there were 2400 towels left")


Simplify. It includes multiplying eq(2) by 2 (both sides).

3x +      w = 4000      (1')
3x + 2x + w = 4800      (2')

or

3x +  w = 4000          (1'')
5x +  w = 4800          (2'')


Now subtract eq(1'') from eq(2''). You will get

2x = 4800-4000 = 800  ====>  x =  = 400.


Answer.  400 red towels;  2*400 = 800 blue towels and 4000 - 400 - 800 = 2800 white towels.