Ta có:220,33-ab,cd=abc,d
220,33-ab,cd=ab,cdx10
220,33=ab,cdx10+ab,cd
220,33=ab,cdx(10+1)
220,33=ab,cdx11
ab,cd=220,33:11
ab,cd=20,03
Vậy abcd=2003
220,33 - ab,cd = 10 x ab,cd
220,33 = ab,cd + 10 x ab, cd
220,33 = ab,cd x (10 + 1)
220,33 = ab,cd x 11
ab,cd = 220,33 : 11
ab,cd = 20,03
=> abcd = 2003
tick nha
2003 la dung minh thi violympic roi