in a store, pencils have one price and pens another. 2 pencils and 3 pens cost .78 but 3 pencils and 2 pens cost .72. how much does 1 pencil cost?
If the prices are x and y cents for pencils and pens, respectively, then you know that
2x+3y = 78
3x+2y = 72
So now just solve for x