(1) Add the two equations together: -2y=48, so y=-24. Now substitute for y in either equation:
x+3y=19⇒x-72=19, x=91. Solution x=91, y=-24.
(2) 9x+3y=-27, so 18x+6y=-54, and -x-6y=20: add these last two equations together:
17x=-34, x=-2. Substitute for x in either equation:
-x-6y=20⇒2-6y=20, -18=6y, y=-3. Solution x=-2, y=-3.