Systems of linear equations are used when we have 2 equations that both contain 2 unknown variables. Since we are trying to find the price of bread and milk, we can let b = num of bread and m = num of milk.
Betty spends $50.73 buying b loaves of bread and m gallons of milk, so the first equation would be 1.39b + 2.49m = 50.73. Betty spends $51.63 buying b loaves of bread and m gallons of milk at Store B, so the second equation is 1.29b + 2.69m = 51.63.
