What is the greatest amount of postage you would not be able to pay using only a combination of seven cent and seventeen cent stamps?
I have done a similar problem and got it correct but I am just wondering if there are other ways to do this. Please help me out thanks
Suppose we can make $n$ cents. If we use two or more $17$s, we can replace two $17$s with five $7$s to make $n+1$. If we use twelve or more $7$s, we can replace twelve $7$s with five $17$s to make $n+1$. If we don't use two $17$s, and we don't use twelve $7$s, how large can $n$ be?
