\[\boxed{\mathbf{21.}}\]
\[37 + 2 = 39 < 40\]
\[37 + 22 = 59 > 40\]
\[37 - 22 = 15 < 40\]
\[4 + 44 = 48 < 50\]
\[14 + 44 = 58 > 50\]
\[44 - 14 = 30 < 50\]
\[77 - 3 = 74 > 60\]
\[77 - 33 = 44 < 60\]
\[77 - 17 = 60\]