Example 10
i̇ find 13 but it says answer is 14 ?

The answer is 14, When 98 is divided by 7 the quotient is 14 when you add three to 98 the muber will be 101 but the question says that it is under 100 so 101 is ruled out so it is obvious that the answer is 13. because 13 numbers are divisible by 7 the last one being 91 + 3= 94 which is less than 100 so you are right with your answer!