\[\boxed{\mathbf{1.}}\]
\[1)\ \]
\[2)\]
\[3)\]
\[\boxed{\mathbf{2.}}\]
\[1)\ 23 - 8 = 15\]
\[15 + 8 = 23 - верно;\]
\[23 - 15 = 8 - верно.\]
\[2)\ 61 - 29 = 42\]
\[42 + 29 = 71 - неверно;\]
\[61 - 42 = 19 - неверно.\]
\[3)\ 84 - 47 = 37\]
\[47 + 37 = 84 - верно;\]
\[84 - 37 = 47 - верно.\]
\[\boxed{\mathbf{3.}}\]
\[1)\ 98 - 59 = 39\ (км).\]
\[2)\ 63 - 25 = 38\ (см).\]
\[3)\ 102 - (26 + 57) =\]
\[= 102 - 83 = 19\ (м).\]
\[4)\ 150 - (48 + 55) =\]
\[= 150 - 103 = 47\ (м).\]