What is the sum of all two-digit numbers that gives a remainder of 3 when they are divided by 7?

Question: What is the sum of all two-digit numbers that gives a remainder of 3 when they are divided by 7? Solution: general formula for that number = 7n + 3 n = 1, then the number is = 7 + 3 = 10 n = 2, then the number is =14 + 3 = 17...n= 13, then the number is = 94sum = 10 + 17 + ... + 94 = 13 (10 + 94)/2 = 676