If anyone is interested in learning mathematics!
First a great resource to start learning most fields but especially mathematics is Khan Academy It has courses in: Early math, arithmetic, pre-algebra, algebra, geometry, trigonometry, intro to statistics, precalculus, calculus, multivariable calculus, differential equations, and linear algebra.
Here also gives you a great set of resources for you to learn beginning mathematics Heres a nice calculator to check your work: Wolfram Alpha
However if you learn better by reading books I’ll link a few pdfs for a couple of fields, these are mostly introductory books and notes.
Pre-algebra: here
Algebra: here
Geometry: here
Trigonometry: here,
Calculus and Multivariable Calculus: here
Differential Equations: here
Linear Algebra: here, here,
Intro to Proof: here, here, here,
Set Theory: here,
Logic: here
Category Theory: here
Group Theory: here
Intro to Abstract Algebra: here
Commutative Ring Theory: here
Intro to Combinatorics and Graph Theory: here
Intro to Algebraic Topology: here
Intro to Topology: here, here,
Convex Geometry: here
Discrete Geometry: here here
Differential Geometry: here
Manifolds: here
Intro to Analysis: here
Intro to Real Analysis: here
Complex Analysis: here
Elementary Number Theory: here
Feel free to add to this with more pdfs for mathematics and more resources to learn!