Let's simplify and solve the equation step by step.
You have the equation:
\[ -2w + 21 = w - 8w + 36 \]
First, simplify the right side:
\[ w - 8w = -7w \]
So the equation becomes:
\[ -2w + 21 = -7w + 36 \]
Next, let’s add \(7w\) to both sides to move all the \(w\) terms to the left:
\[ -2w + 7w + 21 = 36 \]
This simplifies to:
\[ 5w + 21 = 36 \]
Now, subtract \(21\) from both sides:
\[ 5w = 36 - 21 \]
This simplifies to:
\[ 5w = 15 \]
Next, divide both sides by \(5\):
\[ w = \frac{15}{5} = 3 \]
So the solution to the equation is:
\[ w = 3 \]