If a substance has a half-life of one year, how long will it take for half of the substance to decay?

Since wxyz is 4, halfof that would be 2.

The zhou dynasty (1046-256 bce) was the longest-lasting of china's dynasties. it followed the shang dynasty (c. 1600-1046 bce) and it finished when the army of the state of qin captured the city of chengzhou in 256 bce.