What ratio to mix 15% and 30% to get 20%?

Find the number of real number solutions for the equation. x2 + 5x + 7 = 0 0 cannot be determined 1 2

The radius of the earth is two times the radius of the moon. what fraction of the volume of the earth is the volume of the moon?

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.