Ta có :
\(B⋮99\Rightarrow B⋮9,11\) (do \(99=BCNN\left(9,11\right)\)
\(\Leftrightarrow6+2+x+y+4+2+7⋮9\)
\(\Leftrightarrow21+x+y⋮99\)
\(\Leftrightarrow x+y\in\left\{6;15\right\}\)
+) \(B⋮11\Leftrightarrow\left(6+x+4+7\right)-\left(2+y+2\right)⋮11\)
\(\Leftrightarrow\left(17+x\right)-\left(4+y\right)⋮11\)
\(\Leftrightarrow13+x-y⋮11\)
\(\Leftrightarrow13+\left(x-y\right)⋮11\)
\(\Leftrightarrow x-y\in\left\{9;-2\right\}\)
+) \(x-y=9\Leftrightarrow x=9;y=0\) (loại)
+) \(x-y=-2;x+y\in\left\{6;15\right\}\rightarrow\) (loại)
+) \(x+y=6\Rightarrow x=2;y=4\) (TM)
Vậy \(x=2;y=4\)
