Two pencils and one pen cost $0.80, and one pencil and two pens cost $1.15. How many cents would three pencils cost?

Answer 1

2x+y = 80

x+2y = 115

multiply 1st equation by 2 to get 4x+2y = 160, then subtract the 2nd equation to get

4x-x +2y-2y = 160-115

3x = 45 cents for 3 pencils