\[\boxed{\mathbf{38}\mathbf{.}}\]
\[1)\ 27 - 17 = 27 - 10 - 7 =\]
\[= 17 - 7 = 10\]
\[34 - 24 = 34 - 20 - 4 =\]
\[= 14 - 4 = 10\]
\[55 - 35 = 55 - 30 - 5 =\]
\[= 25 - 5 = 20\]
\[57 - 27 = 57 - 20 - 7 =\]
\[= 37 - 7 = 30\]
\[46 - 26 = 46 - 20 - 6 =\]
\[= 26 - 6 = 20\]
\[61 - 51 = 61 - 50 - 1 =\]
\[= 11 - 1 = 10\]
\[75 - 55 = 75 - 50 - 5 =\]
\[= 25 - 5 = 20\]
\[86 - 36 = 86 - 30 - 6 =\]
\[= 56 - 6 = 50\]
\[92 - 22 = 92 - 20 - 2 =\]
\[= 72 - 2 = 70\]
\[2)\ 24 - 21 = 24 - 20 - 1 =\]
\[= 4 - 1 = 3\]
\[36 - 32 = 36 - 30 - 2 =\]
\[= 6 - 2 = 4\]
\[54 - 53 = 54 - 50 - 3 =\]
\[= 4 - 3 = 1\]
\[67 - 62 = 67 - 60 - 2 =\]
\[= 7 - 2 = 5\]
\[49 - 47 = 49 - 40 - 7 =\]
\[= 9 - 7 = 2\]
\[88 - 81 = 88 - 80 - 1 =\]
\[= 8 - 1 = 7\]
\[79 - 76 = 79 - 70 - 6 =\]
\[= 9 - 6 = 3\]
\[87 - 84 = 87 - 80 - 4 =\]
\[= 7 - 4 = 3\]
\[95 - 94 = 95 - 90 - 4 =\]
\[= 5 - 4 = 1\]