With a half life of 28.8 years, how long will it take 1g of strontium-90 to decay to 125mg

Does the construction demonstrate how to copy an angle correctly using technology a) yes the distance between points a and f was used to create circle h b) yes the distance between points f and g was used to create circle h c) no the distance between points a and f was used to create circle h d) no the distance between points f and g was used to create circle h