How can i improve my maths becouse i know noting and am in y9

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?

Eli won $200 in a spelling contest. his mother opened a savings account for him so he could save for a laptop computer. if the bank offers a simple annual interest rate of 4%, how much interest will eli earn over 3 years?

Rewrite f(x)=x^2+8x-20 in the form that would most easily you identify the zeros of the function