Theres a number of passes to purchase
Normal price (without pass) is $6
If Seth goes to all 30 movies without pass he will spend
30x6 = $180 dollars
WITH the pass Seth have $30 dollars , then dividing by 2 , this means he can go to 30/2 = 15 movies in summer with pass
Then remains another 15 movies that he can vo WITHOUT PASS
in this 15 movies Seth spends 15x6= $90 dollars
add this to the $30 spent in the other 15 movie
it gives 30+90 = $120 dollars
Finally substract
$180- $120= $60 dollars he can save