We will need to use a systems of linear equations here. Firstly, we will use x for cans of peas and y for cans of corn. This is kind of difficult to explain, but basically, our first equation is going to be the amount x and y costs. Therefore, 0.85x + 0.78y = 6.59. This works because we need to find out how much cans she bought of each.
Next, we know that she for 2 more cans of peas than cans of corn. We can use the equation, 2 + y = x, to represent this situation. This is because she purchased two more cans of peas, so we add 2 to y (cans of corn).
Our equations are: 0.85x + 0.78y = 6.59, 2 + y = x