Simplify the polynomial
3x^2 + 6 – 2x + 5x – 4x^2 + 9
a –x^2 + 3x + 15
b 7x^2 + 3x + 3
c x^2 – 3x + 15
d –x^2 + 7x + 15

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?

Write two subtraction equations that are equivalent to 5 + 12 = 17.

Two streets intersect at a 30- degree angle. at the intersection, the are four crosswalks formed that are the same length. what type of quadrilateral is formed by the crosswalks?