\[\boxed{\mathbf{9.}}\]
\[28 + 15 = 28 + 10 + 5 =\]
\[= 38 + 5 = 43\]
\[19 + 23 = 19 + 20 + 3 =\]
\[= 39 + 3 = 42\]
\[37 + 16 = 37 + 10 + 6 =\]
\[= 47 + 6 = 53\]
\[49 + 17 = 49 + 10 + 7 =\]
\[= 59 + 7 = 66\]
\[25 + 36 = 25 + 30 + 6 =\]
\[= 55 + 6 = 61\]
\[68 + 24 = 68 + 20 + 4 =\]
\[= 88 + 4 = 92\]
\[34 + 49 = 34 + 40 + 9 =\]
\[= 74 + 9 = 83\]
\[77 + 18 = 77 + 10 + 8 =\]
\[= 87 + 8 = 95\]
\[56 + 26 = 56 + 20 + 6 =\]
\[= 76 + 6 = 82\]