Since there is no feasible region defined, there is no answer possible.
If we knew the values of 'x' and 'y', and the boundaries of the feasible region, we could answer that question quickly and easily.
Unfortunately, limitations of the browser used by Answers.com means that we cannot see most symbols. It is therefore impossible to give a proper answer to your question. Please resubmit your question spelling out the symbols as "plus", "minus", "equals", "squared", "cubed" etc. There is no visible operator between 3x4y unless some of them are meant to be powers. Also, it is necessary to know the feasible region. But since you have not bothered to provide that information, I cannot provide a sensible answer.
8
20 and the vertex of the parabola is at (3, 20)
maximum value of 6y+10y
42
(6x)(5y)
14
The answer obviously depends on what the boundaries of the feasibility region are.
78
Since there is no feasible region defined, there is no answer possible.
It is 18.
The answer depends on the feasible region and there is no information on which to determine that.
2x+2y
If we knew the values of 'x' and 'y', and the boundaries of the feasible region, we could answer that question quickly and easily.
It is 18.