Well, you would need to compensate for the cost of the banquet hall adding an addition $700 to the goal of $1000.
If you need to raise at least $1700 you can write this inequality.
Let x represent the number of tickets sold.
15x≥1700
x≥ 114 (rounded to the nearest whole number because you can't sell half a ticket)
So, at least 114 tickets need to be sold.