hi im in a hurry and i dont get a few problems please help...

-The diffrence between two numbers is 16. Three times the larger number is nine times smaller. What are the numbers? Show some work if you can please....

-A gardener has two kinds of solutions containing weed killer and water. One solution is 5% weed killer and the other solutiion is 15% weed killer. The gardener needs 100 liters of a 12% solution of weed killer and wants to make it by mixing it himself. How much of each solution should he use?

THX FAST PLX!