You can only spend $37, so the total amount you spend needs to be less than or equal to $37. The amount you spend on tapes is going to be equal to the cost per tape. What you will do is take $10 multiplied by the number of tapes you buy (x) - so at this point it would be "10x". The amount you spend on CDs is going to be equal to the cost per CD, so here you will have $13 multiplied by the number of CDs (y), so at this point you will have "13y". Adding these two amounts gives you your total, which must be equal to or less than $37.
Your answer will be -> 10x+13y </=37 (A).
