Corollary 7.2.1.7. Let $f: A \hookrightarrow B$ and $g: B \hookrightarrow C$ be monomorphisms of simplicial sets. If both $f$ and $g \circ f$ are left anodyne, then $g$ is left anodyne. If $f$ and $g \circ f$ are right anodyne, then $g$ is right anodyne.
$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$