Answer:
80 cookies per hour
Explanation:
First, let's make 3 1/2 a decimal, so that would be 3.5. Now lets make this problem a proportion. 280/3.5 means that Stan makes 280 cookies every 3.5 hours.
Let's simply this proportion to find the unit rate. 3.5 divided by 3.5 is 1, so dividing by 3.5 will help find the unit rate. We already did the bottom, so let's do the top. 280 divided by 3.5 is 80.
Therefore the unit rate is 80.
Hope I helped!!!