What is the scale factor of figure B to figure A?

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?

This is different from the first one can someone me

Find the dimensions of the circle. area = 64π in.² r= in.