The cost of the footballs is 8 x $8.00 = $<<8*8=64.00>>64.00
The cost of the basketballs is 18 x $7.00 = $<<18*7=126.00>>126.00
The cost of the softballs is 24 x $5.00 = $<<24*5=120.00>>120.00
The total cost is $64.00 + $126.00 + $120.00 + (36 x $5.00) = $<<64+126+120+(36*5)=478.00>>478.00
Mrs. Weeks paid for the balls using four $100.00 bills which is $400.00
Her change is $400.00 - $478.00 = $<<400-478=78.00>>78.00. Answer: \boxed{78}.