Our review of a trial court's findings of fact is limited to determining whether they are supported by substantial evidence and in turn whether the findings support the trial court's conclusions of law and judgment. Substantial evidence is evidence sufficient to persuade a fair-minded person of the truth of the declared premise. Holland v. Boeing Co., 90 Wn.2d 384, 583 P.2d 621 (1978). *14Appellant contends the trial court erred in finding that the carpeting was substantially destroyed and it was reasonable and proper to replace it. In this case, the property manager, a carpeting repair and maintenance man, and a carpeting salesman testified that the carpeting should have been replaced, and to do so. was reasonable given the quality of the apartment. Opinion testimony may determine the reasonableness of the replacement and its cost. Hellbaum v. Burwell & Morford, 1 Wn. App. 694, 704, 463 P.2d 225 (1969). There was substantial evidence of extensive damage and 100 percent replacement was not unreasonable under the circumstances. We find no error in the finding of the trial court, particularly since a depreciation factor was considered.