Explanation

Step 1: Counting 7s in the ones place

Numbers where 7 appears in the ones place:

7, 17, 27, 37, 47, 57, 67, 77, 87, 97 → 10 times

Step 2: Counting 7s in the tens place

Numbers where 7 appears in the tens place:

70, 71, 72, 73, 74, 75, 76, 77, 78, 79 → 10 times

Step 3: Adjust for double counting

77 has two sevens, so we counted it twice.

Total occurrences:

10 (ones place) + 10 (tens place) = 20 times