Marta and Carmem have won many chocolates each. They mixed all the chocolates and now they no longer know how many chocolates each of them won. Let's help them find out these numbers? It is known that:

(a) together, they won 200 chocolates;

(b) Marta remembers that she won fewer than 100 chocolates, but more than $4 / 5$ of what Carmem won; and

(c) the number of chocolates each of them won is a multiple of 8.
Let $x$ be the number of chocolates Marta won and $y$ be the number Carmem won. We know that $x+y=200, x\frac{4}{5} y$. Therefore, $y \geq 100$ and, consequently, $x>\frac{4}{5} \times 100=80$. Thus, $x$ is an integer between 80 and 100. Since it must be a multiple of 8, it can only be 88 or 96. Let's decide which one it is.

(a) If $x=88$, then $y=200-88=112$. Therefore, $88=x>\frac{4}{5} \times 112=89.6$, which is not possible.

(b) If $x=96$, then $y=200-96=104$ and $96=x>\frac{4}{5} \times 104=83.2$, which is possible. Thus, Marta won 96 chocolates and Carmem 104.