Hey there!
-3w = -21
DIVIDE -3 to BOTH SIDES
-3w/-3 = -21/-3
CANCEL out: -3/-3 because it give you 1
KEEP: -21/-3 because it gives you the w-value
NEW EQUATION: w = -21/-3
SIMPLIFY IT!
w = 7
Therefore, your answer is: w = 7
Good luck on your assignment & enjoy your day!
~Amphitrite1040:)