abcd=2738+ab
=>ab.100+cd=2738+ab
=>ab.100-ab=2738-cd
=>ab.99=2739-cd
Vì cd>9
=>2738-cd<2738-9=2729
=>ab.99<2729
=>ab<28
Vì cd<100
=>2738-cd>2738-100=2638
=>ab.99>2638
=>ab>26
=>26<ab<28
=>ab=27
=>2738-cd=27.99=2673
=>cd=2738-2673
=>cd=65
=>abcd=2765
Vậy a=2,b=7,c=6,d=5