Question 268409
{{{10^51}}} is a 1 followed by 51 zeros. When we subtract 9 from it we will have to borrow. If you think about how borrowing works, you will realize that the 1 at the start will become a zero and that all the zeros except the last one (IOW 50 of them) will become 9's and the last one will become a 10. After we subtract the 9 we will get a 1 at the end with 50 9's in front of it. The sum of 50 9's and a 1 would be 50*9 + 1 = 450 + 1 = 451.