Answer: he can pay for 6 people total (including him)
Step-by-step explanation:
first lets subtract the flat fee from the total amount of money he has
70 - 40 = 30
now lets divide 30 by $4.50 to see how many people he can pay for
30 / $4.50 = about 6.5
obviously you cant pay for half a person so he can invite 5 people (he also has to pay for himself)