4 4 8 5 3 1 5 1 5 8 8 2 2 8 4 9 From the back, double every other number. 8 4 (16) 5 6 1 (10) 1 (10) 8 (16) 2 4 8 8 9 After, we have to de-concatenate the double-digit numbers and then add them to ...