если -12/30-10,8/-3/15-4/+12, вам x=-3

The provided text appears to be a mathematical expression or a set of conditions, but it is not a clearly defined question or problem to solve. It contains fractions, decimals, and an assignment of a variable. Without a specific question (e.g., 'simplify', 'solve for x', 'evaluate'), it's impossible to provide a definitive answer.

If the intention was to evaluate the expression or solve for 'x' under certain conditions, please provide a clear mathematical question.