After 3 half lifes how many c-14 atoms would remain

Halife of C-14 is=14(RAM÷2)

You get=7 but further more let's say after 3 half life as your question stated it may result to decimal something which is impossible (as nucleons never be decimal)

Hence after 3half life it will continue to be 7

i don't know what the picture looks like but i can take a guess and say maybe basidiomycetes?

both anaerobic and aerobic respiration use glucose (or other carbohydrates), proteins and lipids to produce atp and nadh. cell uses those energy molecules, obtained from food and   breaks them down during the chemical reactions of respiration. in anaerobic respiration, nadh is regenerated to nad+ by enzymes lactate dehydrogenase (lactate is produced, e.g. in muscle cells) or by alcohol dehydrogenase where ethanol is produced (alcohol fermentation), while in aerobic respiration, electrons from nadh are deposited in the mitochondria to regenerate nad+ (electron transport chain. anaerobic respiration produces 2 atp per molecule of glucose compared to aerobic respiration where about 38 atp molecules are produced.