\[\boxed{\mathbf{34}\mathbf{.}}\]
\[25 - 12 = 25 - 10 - 2 =\]
\[= 15 - 2 = 13\]
\[36 - 11 = 36 - 10 - 1 =\]
\[= 26 - 1 = 25\]
\[47 - 13 = 47 - 10 - 3 =\]
\[= 37 - 3 = 34\]
\[58 - 15 = 58 - 10 - 5 =\]
\[= 48 - 5 = 43\]
\[43 - 21 = 43 - 20 - 1 =\]
\[= 23 - 1 = 22\]
\[56 - 22 = 56 - 20 - 2 =\]
\[= 36 - 2 = 34\]
\[64 - 31 = 64 - 30 - 1 =\]
\[= 34 - 1 = 33\]
\[77 - 35 = 77 - 30 - 5 =\]
\[= 47 - 5 = 425\]
\[58 - 33 = 58 - 30 - 3 =\]
\[= 28 - 3 = 25\]
\[79 - 42 = 79 - 40 - 2 =\]
\[= 39 - 2 = 37\]
\[86 - 41 = 86 - 40 - 1 =\]
\[= 46 - 1 = 45\]
\[96 - 55 = 96 - 50 - 5 =\]
\[= 46 - 5 = 41\]