Pls help! I suck at math and this could really affect my grade.

While scuba diving, rajeev dove to a depth of 12.6 feet below the surface of the water and then descended another 8.7 feet. what expression can be used to find rajeev's new position? 12.6 – 8.7 –12.6 – 8.7 –12.6 – (–8.7) 12.6 – (–8.7)

Standard deviation of 19,29,21,22,23

Which shows one way to determine the factors of 4x3 + x2 – 8x – 2 by grouping?