A wall in Marcus's bedroom is 8 2/5 feet high and 18 1/3 feet long. If he paints 1/2 of the wall blue, how many square feet will be blue?

The area of the wall is 8 2/5 * 18 1/3 = <<(8 2/5)*(18 1/3)=156>>156 square feet

1/2 of the wall is blue, so the blue area is 1/2 * 156 = <<1/2*156=78>>78 square feet. Answer: \boxed{78}.