First we need to find unit rate, which means how much each postcard cost. Therefore we can do 3.30 divided 6 which give us 0.55 per post card. We can check to see if this is correct by plugging 0.55(6) which gives us 3.30 dollars. Now to find Ms.Robbini you can do 35.20 divided by 0.55 which gives us 64. So now we know that Ms.Robbini spent 35.20 dollars on 64 postcards.
