5/2 = 5:2
Lets take 5:2 as 5x and 2x.
5x + 2x = 140
7x = 140
x = 140/7
x = 20
So, 5x = 5x20 = 100 red bricks
and, 2x = 2x20 = 40 grey bricks.
100 + 40 = 140 bricks
So, to build the decorative wall, 100 red bricks and 40 grey bricks were used.
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