The demand for silver decreases, other things equal, when

The demand for silver decreases, other things equal, when the gold market is suddenly expected to boom.

This is the logical consequence of the fact that silver and gold are used as investment commodities to preserve the value of your assets. If market predicts a quick increase in the prices of gold, the market will sell its assets in silver to purchase assets in gold to make a greater profit.

-2x+8=y=x-1
-2x+8=x-1
add 2x to both sides
8=3x-1
add 1
9=3x
divide 3
3=x
sub
y=x-1
y=3-1
y=2

(x,y)
(3,2)