For the first one, subtracting the membership fee, we have 9 dollars to buy as many 1.50 dollar videos as possible. 9/1.50 works well as 6, so he can buy 6.
Subtract 160 from 480 to get 320, and divide that by 80 to get 4 days
We can do some guess and check here. If he buys 2 t shirts, that's 12*2=24 and 41-24=17. 17 is not a factor of 5, so that doesn't work. If he buys 3, that's 12*3=36 and 41-36=5. 5 is a factor of 5, so that works!