19. No
20. No
21. Yes
23. 1.8 miles
So 4 eggs is 2/3of 6 eggs, so to get the amount of milk we multiply the 3 cups by 2/3 (or just divide by 3 and multiply by 2) and get 2 cups of milk.
Hope this helps!
I believe the answer is C
Half a century is 50 years. a century is 100 years