12b-17b-b=

Simplified, the expression is -6b.

Steps:

• 12b - 17b = -5b
• -5b - b = -6b

If this is part of an equation (e.g., -6b = 0), then b = 0. If -6b = c, then b = -c/6. Let me know the full equation if you want the solve.