Solve 6+5c-2c+7-c equation

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?

An arc subtends a central angle measuring 7pi/4 radians what fraction of the circumference is this arc?

Which of the following circles have their centers in the third quadrant?