What is the half life of an element of 1/8 of a sample remains after 12 years?

Iwould sure like to answer your question but i honestly just don’t know

Independent variable is something that is changed in a experiment. 

Year  1936,  lehman predicted that the earths 'inner core' is solid. she observed that the seismic signals during her study were bent and did not pass through instead bouncing back. later it was confirmed that the earth's inner core was solid made up of nickel-iron and had a molten outer core.