When practical difficulties, unnecessary hardships or results inconsistent with the general intent and purpose of this title occur through the strict application of the provisions of this title to the parcel or group of parcels affected by a common problem, the planning and zoning commission shall have the power to grant, upon such terms and conditions as it deems necessary and proper as may be in harmony with its general intent and purpose, so that the spirit of the title is observed, public safety and general welfare secured, and substantial justice done, variances as to the use provisions of this title. (1987 Code § 17.68.010)