Seven boys hire DVD's and each pays R5,50
I assume R 5.50 ( R to be the currency)
also assuming that they dont hire any more DVDs
total amount paid by 7 boys
= 5.50 × 7
= 38.5
when 4 more friends join the amount should get divided by 11 ( 7 + 4 )
so each has to pay an amount of 38.5 / 11 = 3.5
I think my assumptions here were correct
if not
let me know :)