\[\boxed{\mathbf{24.}}\]
\[83 + 17 = 83 + 10 + 7 =\]
\[= 93 + 7 = 100\]
\[65 + 35 = 65 + 30 + 5 =\]
\[= 95 + 5 = 100\]
\[48 + 52 = 48 + 50 + 2 =\]
\[= 98 + 2 = 100\]
\[26 + 34 = 26 + 30 + 4 =\]
\[= 56 + 4 = 60\]
\[59 + 41 = 59 + 40 + 1 =\]
\[= 99 + 1 = 100\]
\[37 + 63 = 37 + 60 + 3 =\]
\[= 97 + 3 = 100\]
\[42 + 18 = 42 + 10 + 8 =\]
\[= 52 + 8 = 60\]
\[71 + 29 = 71 + 20 + 9 =\]
\[= 91 + 9 = 100\]
\[56 + 34 = 56 + 30 + 4 =\]
\[= 86 + 4 = 90\]
\[39 + 31 = 39 + 30 + 1 =\]
\[= 69 + 1 = 70\]
\[62 + 38 = 62 + 30 + 8 =\]
\[= 92 + 8 = 100\]
\[15 + 75 = 15 + 70 + 5 =\]
\[= 85 + 5 = 90\]