Can someone answer this and please give an explanation? It's just to further my understanding.

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)

What is the name used to describe a graph where for some value of x, there exists 2 or more different values of y?

The border line of the linear inequality 4x + 7y < 5 is dotted true or false?