Final answer:
The system of equations that matches the night at the movies for the three families is 3x+2y+5z=85.
Step-by-step explanation:
The system of equations that matches the night at the movies for the three families is b) 3x+2y+5z=85. Let's assign variables to each item: x is the price of one tub of popcorn, y is the price of one plate of nachos, and z is the price of one drink. Based on the information given, the Smiths spent $65 which can be represented by the equation 2x+y+3z=65. The Langes spent $85 which can be represented by the equation 3x+2y+5z=85. The Radfords spent $40 which can be represented by the equation x+y+2z=40. Therefore, the correct equation is 3x+2y+5z=85.