To find out how many pork sliders were sold, we need to subtract the number of beef sliders and vegetable sliders from the total number of sliders sold.
The number of beef sliders sold is 20% of 120 sliders, which is (20/100) * 120 = 24 sliders.
The number of vegetable sliders sold is 15% of 120 sliders, which is (15/100) * 120 = 18 sliders.
Now, let's subtract the number of beef and vegetable sliders from the total number of sliders sold:
Total sliders sold - Beef sliders - Vegetable sliders = Pork sliders
120 sliders - 24 sliders - 18 sliders = Pork sliders
120 sliders - 42 sliders = Pork sliders
78 sliders = Pork sliders
Therefore, 78 pork sliders were sold.