Which of the following statements are true?

How many kilograms of a 5% salt solution and how many kilograms of a 15% salt solution must be mixed together to make 45kg of an 8% salt solution?

The floor of a building consists of 3000 tiles which are rhombus shaped and each of it's diagonals are 45 cm and 30 cm in length. find the total cost of polishing the floor, if the cost per m² is rs. 4.

Determine the equivalent system for the given system of equations: 5x − 3y = 6 x + y = 2