Verified Answer :

let's call iggy "i".

5 i - 8 <= 72 // add 8 to both sides
5
i <= 80 // divide by 5. Since 5 is positive, we do not flip the inequality.
i <= 16

Iggy has 16 or less marbles.

alexak

n = the number of marbles that iggy has
5n - 8 ≤ 72
5n ≤ 80
n ≤ 16
n ≤ 16 marbles

So, Iggy has 16 marbles or less.

Answer: Iggy has 16 marbles or less.