\[\boxed{\mathbf{5.}}\]
\[20 + 8 = 28\]
\[40 + 5 = 45\]
\[70 + 2 = 72\]
\[30 + 6 = 36\]
\[60 + 3 = 63\]
\[90 + 7 = 97\]
\[50 + 9 = 59\]
\[80 + 1 = 81\]
\[60 + 6 = 66\]