Definition: $M$ is projective iff for every surjective morphism $f:A\rightarrow B$, and every morphism $g:M\rightarrow B$ there is morphism $h:M\rightarrow A$ such that $fh=g$.
Now if $M$ is free with base $\{x_i\}$ then we can define $g$ setting $x_i\mapsto a_i\in f^{-1}(g(x_i))$.
Definition: $M$ is projective iff for every surjective morphism $f:A\rightarrow B$, and every morphism $g:M\rightarrow B$ there is morphism $h:M\rightarrow A$ such that $fh=g$.
Now if $M$ is free with base $\{x_i\}$ then we can define $g$ setting $x_i\mapsto a_i\in f^{-1}(g(x_i))$.