thinking

• Rack your brains

  To think very hard and intensely, often for an extended period, in an attempt to remember something or solve a difficult problem.

• A no-brainer

  A no-brainer is a decision or solution that is so obvious or easy it requires little to no thought.

• To pace back and forth

  To repeatedly walk a short distance in one direction and then the opposite, often indicating nervousness, impatience, or deep thought.