subtract the last numbers first 3-1 which is 2 then 2-6 which is impossible so you borrow from 5 and add 10 to 2 which become 12-6 which is 6 the the first number has only 4 left because you borrowed from it which is 4 so 523-61= 462.
subtract the last number 6-7 it not possible because 6 is less than 7 so borrow from 5 then add 10 to 6 which become 16-7=9 then the second number you have 4-8 since you borrowed from 5, 4-8 is also not possible so borrow from 4 which become 14-8 which is 6 and the first number which is now 3- 1 which is 2 so all the result become 269
