\[\boxed{\mathbf{3.}}\]
\[32 + 15 = 32 + 10 + 5 =\]
\[= 42 + 5 = 47\]
\[27 + 11 = 27 + 10 + 1 =\]
\[= 37 + 1 = 38\]
\[43 + 12 = 43 + 10 + 2 =\]
\[= 53 + 2 = 55\]
\[64 + 13 = 64 + 10 + 3 =\]
\[= 74 + 3 = 77\]
\[24 + 23 = 24 + 20 + 3 =\]
\[= 44 + 3 = 47\]
\[43 + 21 = 43 + 20 + 1 =\]
\[= 63 + 1 = 64\]
\[55 + 32 = 55 + 30 + 2 =\]
\[= 85 + 2 = 87\]
\[62 + 25 = 62 + 20 + 5 =\]
\[= 82 + 5 = 87\]
\[72 + 21 = 72 + 20 + 1 =\]
\[= 92 + 1 = 93\]
\[83 + 15 = 83 + 10 + 5 =\]
\[= 93 + 5 = 98\]
\[56 + 33 = 56 + 30 + 3 =\]
\[= 86 + 3 = 89\]
\[16 + 51 = 16 + 50 + 1 =\]
\[= 66 + 1 = 67\]