two digits with the sum of 7 are 16, 25, 34, 43, 52, 61, and 70
400 more than the original number
400 + 16 = 416 thus 4 + 1 + 6 = 11
400 + 25 = 425 thus 4 + 2 + 5 = 11
400 + 34 = 434 thus 4 + 3 + 4 = 11
400 + 43 = 443 thus 4 + 4 + 3 = 11
400 + 52 = 452 thus 4 + 5 + 2 = 11
400 + 61 = 461 thus 4 + 6 + 1 = 11
400 + 70 = 470 thus 4 + 7 + 0 = 11
my answer is 11