Which of the following has no solution (picture attached)

Bismuth-210 is an isotope that radioactively decays by about 13% each day, meaning 13% of the remaining bismuth-210 transforms into another atom (polonium-210 in this case) each day. if you begin with 233 mg of bismuth-210, how much remains after 8 days?

Me. i can't figure out this question. give an explanation too. .

Micheal is 4 times as old as brandon and is also 27 years older than brandon. how old is micheal