Hey there!
k - 16 = 4
ADD 16 to BOTH SIDES
k - 16 + 16 = 4 + 16
CANCEL out: -16 + 16 because it give you 1
KEEP: 4 + 16 because it give you the x-value
NEW EQUATION:
k = 4 + 16
k = 16 + 4
SIMPLIFY IT!
k = 20
Therefore, your answer is: k = 20
Good luck on your assignment & enjoy your day!
~Amphitrite1040:)