3 dinosaurs laid some eggs. They laid 19 altogether. How many did they each lay?

This challenge is to find as many ways as possible of making 12 using three number cards and the add, subtract and multiply signs.

Can you put the numbers 1 to 9 in the diagram so that the difference between each pair of joined numbers is odd?

How many ways can three runners cover a distance of 19 miles? They all have to run an odd number of miles.