ab5 = ab + 104
ab x 10 +5 = ab x 1 +104
ab x 9 + 5 = 104
ab x 9 = 104 - 5
ab x 9 = 99
ab = 99 : 9
ab = 11
vậy ab=11
k chắc nha
ab5 = ab + 104
100a + 10b + 5 = 10a +b + 104
100a + 10b = 10a + b + ( 104 - 5 )
100a + 10b = 10a + b + 99
( 100a - 10a ) + ( 10b - b ) = 99
90a + 9b = 99
10a + b = 99 : 9
10a + b = 11
a = 1 ; b = 1