What is the distance of (-10,-8), (4,0)

Don't you mean "distance between () and () ?"

Use the distance formula. First, find the difference between the given y values:

8 units. Next, find the difference between the given x values: 14.

Then the desired distance is

d = sqrt (8^2 + 14^2) = sqrt (260) = sqrt (4*65) = 2sqrt (65) (answer)