First, you must determine how much birdseed the volunteer has in cups. To do this, multiply the 12 pounds by the 3 1/4 cups, as there are 3 1/4 cups in one pound. This means the volunteer has 39 cups of birdseed.
Then you must divide the amount of birdseed the volunteer has (39 cups) by the amount of birdseed needed to fill a bird feeder (3/4 cups), which will give you the amount of bird feeders the volunteer can fill (52 bird feeders).
Let x be a random variable representing the mean saraly of professors at two year institutions, then P(x > 55000) = 1 - P(z < (55000 - 52500)/4000) = 1 - P(z < 0.625) = 1 - 0.73401 = 0.26599
