Price of bottled water - $3.50 each price of bag of trail mix - $4 each number of bottles of water sold - x number of bags of trail mix sold - y cost spent for bottles - 3.5x cost spent for bags - 4y total cost; 3.5x + 4y = 1475 ----> 1) total number of items x + y = 400---2) multiply 2nd equation by 4 4x + 4y = 1600 ---> 3) Subtract third equation from the 1st 0.5x = 125 x = 250 when x = 250 x + y = 400 250 + y = 400 y = 150 number of bottles - 250 number of bags - 150