Simplify . Help me ASAP please

Based on what i know about mean, this doesn't add up.

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)

Find the roots of the equation below. x^2 - 6 + 9 = 0