A total of 130 red notebooks and white notebooks are in a container. The ratio of red notebooks to white notebooks was 4 : 9. Some brown notebooks and silver notebooks were put into the container. For every 5 white notebooks that were already in the container, 2 silver ones were added. Then, the final number of red notebooks and brown notebooks was ³₇ the final number of white notebooks and silver notebooks. Find the total number of brown and silver notebooks.

Brown notebooks	Red notebooks	White notebooks	Silver notebooks
	4x5	9x5
		5x9	2x9
3x9		7x9
7 u	20 u	45 u	18 u

The number of white notebooks is repeated.  Make the number of white notebooks the same.  LCM of 9 and 5 is 45.

The total number of white notebooks and silver notebooks is repeated.  Make the total number of white and silver notebooks the same.  LCM of 63 and 7 is 63.

Total number of red notebooks and white notebooks
= 20 u + 45 u
= 65 u

65 u = 130

1 u = 130 ÷ 65 = 2

Total number of brown and silver notebooks
= 7 u + 18 u
= 25 u
= 25 x 2
= 50

Answer(s): 50