。
I have a natural talent for math.
Literal
I [topic-は] by-birth math [of-の] talent [subject-が] exist.
生まれつき ('by birth, inherently, naturally') is an adverb describing inherent qualities. Distinct from natural talent vs. learned skill — 生まれつき implies the quality was present from birth. 数学の才能 uses の to specify the domain of talent ('talent FOR math').