\[\boxed{\mathbf{52.}}\]
\[1)\ 100 + 20 = 120\]
\[120 - 20 = 100\]
\[120 - 100 = 20\]
\[2)\ 100 + 2 = 102\]
\[102 - 2 = 100\]
\[102 - 100 = 2\]