\[\boxed{\mathbf{3.}}\]
\[40 - 2 = 38\]
\[40 - 4 = 36\]
\[40 - 6 = 34\]
\[40 - 8 = 32\]
\[50 - 2 = 48\]
\[50 - 3 = 47\]
\[50 - 5 = 45\]
\[50 - 6 = 44\]
\[70 - 3 = 67\]
\[70 - 4 = 66\]
\[70 - 6 = 64\]
\[70 - 8 = 62\]
\[90 - 1 = 89\]
\[90 - 4 = 86\]
\[90 - 5 = 85\]
\[90 - 9 = 81\]