B:Y:G = 3x:7x:8x.

3x + 7x + 8x = 18x = 90 --> x= 5.

G - B = 8x - 3x = 5x = 25.

Answer: A.
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Blue ......... Yellow ........ Green ......... Total

3x ............... 7x ............. 8x ............... 90

Require to find 8x - 3x = 5x

18x = 90

\(5x = \frac{90}{18} * 5\)

= 25

Answer = A

I would say sub 600.

The ratio of blue disks to yellow disks to green disks in this bag is 3 : 7 : 8, which means that for every 3 blue disks, we have 7 yellow disks, and 8 green disks. Since this is a ratio, we can let the number of blue disks in the bag be 3x, the number of yellow disks be 7x, and the number of green disks be 8x. So 3x + 7x + 8x = 90. If we simplify the equation we get 18x = 90. We can then divide both sides by 18. So . In order to solve for the number of disks, replace x with 5. Therefore the number of green disks is 8x = 8(5) = 40 and the number of blue disks is 3x = 3(5) = 15. The number of green disks is greater than the number of blue disks by 40 - 15 = 25.
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As blue, yellow & green disks are in the ratio of \(3:7:8\), we have to find \(Green-Blue\),
so
\(blue=3x\)
\(yellow=7x\)
\(green=8x\)
as given: \(3x+7x+8x=90\)
\(18x=90\)
\(x=5\)
\(Green=8*5=40\)
\(Blue=3*5=15\)
\(Green-Blue=40-15=25\)

Answer A