8% means 0.08 "of" usually means"times" in math 8% of 10,000 = 0.08 x 10,000 = <em>800 .</em>
I don't understand what "10,000 of 1 year" means. But again, "of" usually means"times" in math. So maybe your question means "0.08 x 10,000 x 1 year" = <em>800 years