(-1,5) , (-2,-6) and (-3,-7)
Let's plot that system below:
5x – 3y < 12
x - 4y > 16
The solutions will be located at the darker blue area
So we can locate three solutions, (-1,5) , (-2,-6) and (-3,-7)
Like this:
Let's test them
(-1,-5)
5(-1) -3(-5) <12
10 < 12 True
(-1) -4(-5)>16
-1 +20>16
19>16 True
(-2,-6)
5(-2) -3(-6) <12
-10+18<12 True
-2 -4(-6) >16