The inequality must be
Then We are going to replace the total budget as total cost T, and as we want to know the number of guests. We need to use the following equation
225 + 12 G = 1000
Then We are going to isolate the term with G
12G = 1000 - 225
12 G = 775
Isolating G
G = 775 / 12 = 64.6
Since we can not have a number of guests that is not an integer, we have to take the integer part of the number
So the answer must be 64 Guests.