Twelve gallons of a salt solution consists of 25% salt. It is the result of mixing a 30% solution with a 20% solution. How many gallons of each of the solutions was used? Let x= the number of gallons of the 30% solution and y= the number of gallons of the 20% solution. The corresponding modeling system is {x+y=120.3x+0.2y=0.25(12). Solve the system by using the method of substitution.

Amira is painting a rectangular banner 2 1/4 yards wide. the banner will have a blue background. amira has enough paint to cover 1 1/2 square yards of the wall. the school colors are blue and yellow, so amira wants to add yellow rectangles on the left and right sides of the blue rectangle. the yellow rectangles will each be 3/4 yards wide and the same height as the blue rectangle. what will be the total area of the two yellow rectangles?