Step 1) Subtract #color(red)(8)# from each side of the equation to isolate the #k# term while keeping the equation balanced:
#-color(red)(8) + 8 - 3/8k = -color(red)(8) - 4#
#0 - 3/8k = -12#
#-3/8k = -12#
Step 2) Multiply each side of the equation by #-color(red)(8)/color(blue)(3)# to solve for #k# while keeping the equation balanced:
#-color(red)(8)/color(blue)(3) xx -3/8k = -color(red)(8)/color(blue)(3) xx -12#
#-cancel(color(red)(8))/cancel(color(blue)(3)) xx -color(blue)(cancel(color(black)(3)))/color(red)(cancel(color(black)(8)))k = -color(red)(8)/color(blue)(3) xx -(3 xx 4)#
#k = -color(red)(8)/cancel(color(blue)(3)) xx -(color(blue)(cancel(color(black)(3))) xx 4)#
#k = 32#