Appellant Docassist, LLC, (“Docassist”), appeals from the trial court’s denial of its motion for summary judgment and entry of summary judgment in favor of Appel-lees, based upon a determination that Do-cassist failed to properly admit a number of new members to the company. We affirm, and reject Docassist’s argument that an August 29, 2011 Letter Agreement serves as evidence of the Board of Managers’ consent to admit new members to Docassist. All parties agree that the Letter Agreement is unambiguous. The express language of the Letter Agreement neither names the new members nor specifies adjustments to the company’s equity resulting from new member capital investment. The Letter Agreement, by its terms, evinces an intent only to raise new capital for the company. Given the unambiguous nature of the Letter Agreement, *1055 Docassist may not rely on extrinsic evidence to support its contentions. See Real Estate Value Co., Inc. v. Carnival Corp., 92 So.3d 255, 260 (Fla. 3d DCA 2012).

We also affirm the trial court’s determination that the subsequent actions taken by Docassist, through its October 25, 2011 and December 7, 2011 amendments to its Operating Agreement, were invalid. The October 25th Amendment is invalid because the Board of Managers did not properly consent to it pursuant to the terms of the company’s Operating Agreement. As a consequence, the subsequent December 7th Amendment (which necessarily was premised upon the validity of the October 25th Amendment) is likewise invalid.

Affirmed.