Ayield sign measures 30 inches on all three sides. what is the area of the sign

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?

With both problems. a.s.a.p directions on photo ^

How do i put 3(x+7) in distributive property