Need math help with A man who has $480 in the denominations of one-rupee notes

Need math help with A man who has $480 in the denominations of one-rupee notes

A man has  $480 in the denominations of one-rupee notes, five-rupee notes and ten-rupee notes. The number of notes of each denomination is equal. What is the total number of notes that he has

ii   There are two examinations rooms A and B. If 10 students are sent from A to B, then the number of students in each room is the same. If 20 candidates are sent from B to A, then the number of students in A is double the number of students in B. The number of students in room A is

iii   The price of 10 chairs is equal to that of 4 tables. The price of 15 chairs and 2 tables together is Rs. 4000. The total price of 12 chairs and 3 tables is

iv   If ab = 3 and a2 + b2 = 29, find the value of ab

v The price of 2 T-shirt and 4 shirts is $1600. With the same money one can buy 1 T-shirt and 6 shirts. If one wants to buy 12 shirts, how much shall he have to pay