The formula for calculating the distance between two points is:
#d = sqrt((color(red)(x_2) - color(blue)(x_1))^2 + (color(red)(y_2) - color(blue)(y_1))^2 + (color(green)(z_2) - color(green)(z_1))^2)#
Substituting the values from the points in the problem and calculating gives:
#d = sqrt((color(red)(-8) - color(blue)(7))^2 + (color(red)(1) - color(blue)(3))^2 + (color(green)(-1) - color(green)(-6))^2)#
#d = sqrt((color(red)(-8) - color(blue)(7))^2 + (color(red)(1) - color(blue)(3))^2 + (color(green)(-1) + color(green)(6))^2)#
#d = sqrt((-15)^2 + (-2)^2 + (5)^2)#
#d = sqrt(225 + 4 + 25)#
#d = sqrt(254) = 15.94# rounded to the nearest hundredth