What value should come in the place of question mark (?) in the following questions?
For the following questions answer them individually
Cost of 36 pens and 42 pencils is Rs.460/-. What is the cost of 18 pens and 21 pencils?
The ratio of the ages of A and B seven years ago was 3 : 4 respectively. The ratio of their ages nine years from now will be 7 : 8 respectively. What is B’s age at present?