The children have visited an alien planet. On the planet they met some friendly aliens with different numbers of eyes. Some have one eye and some have two eyes. Altogether there were ten eyes. How many different combinations of aliens can there be? Perhaps 1+2+1+2+1+2+1 or 2+2+2+2+2.
How about if there were 13 or 19 eyes? What if the aliens had 3 and 5 eyes what would the combinations be?