You need to separate the knowns and unknowns to opposites sides of the equation.
Add 4p to each side: 28>8+4p. Now subtract 8 from each side: 20>4p. Divide through by 4: 5>p, so p<5. That's it! The inequality is satisfied for all values of p less than 5. Let's try p=4. -16+28 is the same as 28-16=12, which is greater than 8, which is true.