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Solution
$$X+Y=3, XY=2,$$
$$(X+Y)^2=9$$
$$(X+Y)^2 = X^2+2XY+Y^2$$
$$X^2+Y^2 = 9-4 =5$$
$$(X-Y)^2 = X^2-2XY+Y^2$$
$$(X-Y)=1$$
$$X^3-Y^3 = (X-Y)(X^2+Y^2+XY)$$
$$=1\times (9-2) = 7$$
Option A is correct.
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