The half life of a substance is 49 years. If there are 220 mg present now, how much will remain in 58 years?

The world’s total consumption of natural gas was 1824 million tons oil equivalent (mtoe) in 1994. The reserves at the end of that year were estimated to be 128 300 mtoe. If consumption had increased by 2% in each of the coming years, and no new sources were ever discovered, how much longer would these reserves have lasted?