90-30+. =66

It looks like you're trying to solve the equation \(90 - 30 + . = 66\).

Let's simplify the left side:

1. Start with \(90 - 30\) which equals \(60\).
2. So, the equation becomes \(60 + . = 66\).

To find the value of the dot (.), we can subtract 60 from both sides:

\[ . = 66 - 60 \]

\[ . = 6 \]

Thus, the value that should replace the dot (.) is \(6\).