3abc = abc x 5
3000 + abc = abc x 5
3000 = abc x 5 - abc
3000 = abc x (5 - 1)
3000 = abc x 4
abc = 3000 : 4
abc = 750
3abc= abcx5
3000+abc=abcx5
3000=abcx5-abc
3000=abcx(5-1)
3000=abcx4
=>abc=3000:4= 750
3abc = abc x 5
3000 + abc = abc x 5
3000 + abc = abc x ( 4+1 )
3000 + abc = abc + abc x 4
3000 = abc x 4 ( Hai tổng bằng nhau cùng bớt đi abc )
abc = 3000 : 4
abc = 750