Gizmo can eat 2 bowls of kibbles in 3 minutes. Leo can eat one bowl of kibbles in 6 minutes. Together, how many bowls of kibbles can Gizmo and Leo eat in 10 minutes?

Gizmo eats two bowls in 3 minutes, which means in a minute he would eat a fraction of 2/3 of the bowl.
On the other hand, leo eats one bowl in 6 minutes hence in a minute he eats a fraction of 1/6 of a bowl. 
When both combine, then in one minute they can eat a fraction of 2/3+1/6= 5/6.
Therefore, in ten minutes they will take 10× 5/6 = 8.333 equivalent to 8 bowls and a third of a bowl