Answer:
All satisfy the conditions
Step-by-step explanation:
Interpreting (x,y) as (movies, video games) then each of these points work.
He must buy 9 items at least and spend $400. Each of these options are more than 9 items and their prices add to $400.
(5,6) = 5(20) + 6(50) = 100+300=400
(10,4) = 10(20) + 4(50) = 200+200=400
(20,0) = 20(20) + 0(50) = 400+0=400
(15,2) = 15(20) + 2(50) = 300 + 100 = 400
