Hey there!
18 = -k + 3
-k + 3 = 18
-1k + 3 = 18
SUBTRACT 3 to BOTH SIDES
-1k + 3 - 3 = 18 - 3
SIMPLIFY IT!
-1k = 18 - 3
-1k = 15
DIVIDE -1 to BOTH SIDES
-1k/-1 = 15/-1
SIMPLIFY IT!
k = 15/-1
k = -15
Therefore, the answer is: k = -15
Good luck on your assignment & enjoy your day!
~Amphitrite1040:)