If two pounds of apples cost $3.00 you can buy 6 pounds for $9.
3÷2 = 1.5, so you can buy 1 lb of apples for $1.50
9 ÷ 1.5 = 6, so you can buy 6 lbs of apples for $9
There are 16 ounces in a pound, so 6 pounds is equal to 96 ounces (6*16)
96 ÷ 5 is 19.2
You cant buy 0.2 apples, so 19.2 must be rounded down to 19 apples
You can buy 19 apples for nine dollars.