Friend #1 gets at least 2/5 of a pizza.
Friend #2 gets at least 2/5 .
Friend #3 gets at least 2/5 .
Friend #4 gets at least 2/5 .
Friend #5 gets at least 2/5 .
Friend #6 gets at least 2/5 .
Sum . . . . . . . . . at least 12/5 of a pizza.
Simplify . . . . . . at least 2.4 pizzas.
-- If pizzas can be bought by the half, they should order at least <em>2-1/2 pizzas.</em>
-- If only whole pizzas have to be ordered, then they should order at least <em>3 pizzas.</em>
A selective breeding. Put your best animals together to get better offspring.
Answer:circulatory system
