It is called a ray. Which is what you described
125 > 50 + 4.25*p
subtract 50 from each side
75 =>4.25p
divide by 4.25
p>17.64
He may invite up to 17 people ( if he doesn't have to pay for himself)
He may invite 16 if he has to pay for himself
The answer to the equation is X= 27