Question

abc x 9 = 1abc

Answer 1

abc x 9 = 1abc 
<=> abc x 9 = 1000 + abc 
<=> abc x 9 - abc = 1000 
<=> 8 x abc= 1000 
<=> abc = 1000/8 
<=> abc = 125

Answer 2

abc x 9= 100+abc 

abcx9-abc=1000

8xabc=1000

abc=1000:8=125