The first step to solving this equation is to expand the term in parenthesis by multiplying each term within the parenthesis by #color(red)(-3)#:
#-20 - 7k = (color(red)(-3) * k) + (color(red)(-3) * -4)#
#-20 - 7k = -3k + 12#
Now, using the necessary mathematics we can isolate the #k# terms on one side of the equation and the constants on the other side of the equation while keeping the equation balanced:
#-20 - 7k + color(red)(3k + 20) = -3k + 12+ color(red)(3k + 20)#
#-20 + color(red)(20) - 7k + color(red)(3k) = -3k + color(red)(3k) + 12+ color(red)(20)#
#0 - 7k + 3k = 0 + 12+ 20#
#-7k + 3k = 12+ 20#
Next, we can combine like terms:
#(-7 + 3)k = 32#
#-4k = 32#
Finally, we can solve for #k# while keeping the equation balanced:
#(-4k)/(color(red)(-4)) = 32/(color(red)(-4))#
#(-4)/(color(red)(-4))k = -8#
#1k = -8#
#k = -8#
