#The question is#

Calculate the dubble integral where D is an area enclosed by the following lines, ,, and

I have tried doing it the following way but its wrong and I cant seem to get it working. Any help would be appreciated

NIntegrate[ Boole[-9 <= 6 x + 5 y <= 9 && -7 <= 3 x + 6 y <= 7], {x, -Infinity, Infinity}, {y, Infinity, Infinity} ]