Jazmyn uses 2 gallons of paint to paint 5 walls. He uses 4 gallons of paint to paint 10 walls. How many gallons of paint does he use per wall?

Gabriel determined that his total cost would be represented by 2.5x + 2y – 2. his sister states that the expression should be x + x + 0.5x + y + y – 2. who is correct? explain.