\[\boxed{\mathbf{3.}\mathbf{212}}\]
\[\textbf{а)}\ 5 \cdot 7 \cdot s = (5 \cdot 7) \cdot s = 35s\]
\[\textbf{б)}\ 7 \cdot p \cdot 32 = (7 \cdot 32) \cdot p =\]
\[= 224p\]
\[\textbf{в)}\ q \cdot 13 \cdot 18 = (13 \cdot 18) \cdot q =\]
\[= 234q\]