Please help this makes no sense

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?

Acarnival sold tickets for $1.50 for adults and $1.00 for students. there were 54 tickets sold for a total of $70.50. write a system of equations to represent the number of adult tickets,x, and the number of student tickets,y. find the solution and explain what it means. i'll you if you me

Rectangle bcde is similar to rectangle vwxy. what is the length of side vy? a) 1 7 b) 2 7 c) 3 7 d) 4 7