\[\boxed{\mathbf{19.}}\]
\[\textbf{а)}\ 14 + 50 = 64\]
\[38 - 1 = 37\]
\[2 + 25 = 27\]
\[61 - 40 = 21\]
\[75 - 5 = 70\]
\[39 + 1 = 40\]
\[90 + 10 = 100\]
\[50 - 1 = 49\]
\[83 + 0 = 83\]
\[\textbf{б)}\ 46 - (2 + 18) = 46 - 20 =\]
\[= 26\]
\[(4 + 16) + 37 = 20 + 37 = 57\]
\[100 - (20 - 19) = 100 - 1 = 99\]