DUE IN 2 HOURS!! :( Help me?

1. Roman mixes 12 liters of 8% acid solution with a 20% acid solution, which results in a 16% acid solution. Find the number of liters of 20% acid solution in the new mixture. Construct a table to organize the information, and show all of your work to solve the problem.

2. The length of a rectangle is 5 mm longer than its width. Its perimeter is more than 30 mm. Let w equal the width of the rectangle.
a. Write an expression for the length in terms of the width.
b. Use expressions for the length and width to write an inequality for the perimeter, on the basis of the given information.
c. Solve the inequality, clearly indicating the width of the rectangle.

3. Solve the system of equations using linear combination.