Hello,
To solve this, we should first write an inequality.
Since we have to pay $109.50 to rent the studio, we will start with that.
Then, we add on 15 per person. Finally, it needs to be under $319.
The inequality is:
109.5 + 15x < 318
Solve it gives:
15x < 208.5
x < 13.9
We have to invite less than 13.9 people. So they most we can invite is only 13.
I hope this helps,
MrEQ