Stephanie had seven add an 8 pound of bird seed she use three out of 8 pound to fill a bird feeder f stephanie had 7 pound of bird seed she use three and 8 pound to fill a bird feeder how much birdseed does stefani have left

So if I understand correctly, she had 7 1/8 pounds of birdseed and used 3/8 pound.
Convert the 7 1/8 to an improper fraction [(8*7)+1]/8 =57/8
57/8 - 3/8 = 54/8, which is 6 6/8 which reduces to 6 3/4 pounds left

If she had 7 pounds of birdseed and used 3/8 pounds, you need to find a common denominator to subtract if you can't do it in your head. 8 would be the common denominator, so:
56/8 - 3/8 = 53/8, which is 6 5/8 pounds left