How many two-digit numbers are divisible by 3 but not by 7?

Sum of two numbers is 15 and sum of their reciprocals is $$ {15\over56}$$. The two numbers are

In a school $${1\over10} $$ of the boys are same in number as $${1\over4}$$ of the girls and  $${5\over8} $$ of the girls are same in number as $${1\over4}$$   of the boys. The ratio of the boys to girls in that school is: 

When n is divided by 6, the remainder is 4. When 2n is divided by 6, the remainder is : 

A number x when divided by 289 leaves 18 as the remainder. The same number when divided by 17 leaves y as a remainder. The value of y is 

A, B, C and D purchase a gift worth Rs. 60. A pays $${1\over2} $$ of what others are paying. B pays $${1\over 3} $$ of  what others are paying and C  pays $${1\over 4} $$ of what others are  paying. What is the amount paid by D?

The difference of a number consisting of two digits from the number formed by inter changing the digits is always divisible by: 

The total number of integers between 100 and 200, which are divisible by both 9 and 6, is