Given expression : 3⋅(1-210-3)+12.
In order to evaluate the given expression, we need to apply order of operations.
According to order of operations we need to simplify parenthesis part first.
We have 1-210-3 inside parenthesis.
Therefore, 1-210-3 = -209-3 = -212.
3⋅(1-210-3)+12 => 3 ⋅(-212) +12.
Now, multiplying 3 and -212, we get -636.
3 ⋅(-212) +12 => -636 + 12
= -624.
Therefore, 3⋅(1-210-3)+12 = -624.