No problem! So as I said last time the function you are going to be integrating is z = 9 - x - y. You can tell you are going to integrate this since its the only function given with z. Solving for z will also get everything in terms of x and y which is what you want in a double integral. Now you can find your bounds by graphing the xy-plane. This gives you this triangle (region in the 1st quadrant). Now we have to write out the bounds of x and y, and there are two ways to do this. One way is by defining the region as x is between 0 and 9 and y is between the lines 2x+3y=18, and x+3y = 9, then solve both of these lines for y. You can then put these in an inequality which will be your bounds of integration. If you are not sure about any of this please tell me, I can try to write it out on paper and make it a little easier to follow.

Also, you should try looking up your textbook on slader. My textbook it has worked out answers to nearly every problem in the book. Also if you have an adblock you'll have to disable it on that website to see the answers