The absolute value function takes any negative or positive term and transforms it to its non-negative form. Therefore, we must solve the term within the absolute value function for both its negative and positive equivalent.
#-8 <= 3d - 1 <= 8#
First, add #color(red)(1)# to each segment of the system of inequalities to isolate the #d# term while keeping the system balanced:
#-8 + color(red)(1) <= 3d - 1 + color(red)(1) <= 8 + color(red)(1)#
#-7 <= 3d - 0 <= 9#
#-7 <= 3d <= 9#
Now, divide each segment by #color(red)(3)# to solve for #d# while keeping the system balanced:
#-7/color(red)(3) <= (3d)/color(red)(3) <= 9/color(red)(3)#
#-7/3 <= (color(red)(cancel(color(black)(3)))d)/cancel(color(red)(3)) <= 3#
#-7/3 <= d <= 3#
Or
#d >= -7/3# and #d <= 3#
Or, in interval notation:
#[-7/3, 3]#