Production by Mexico is the same percentage (3%) of world production for the years of interest, so the relation is
... (mexico production) = 0.03 × (world production)
Then, dividing by 0.03, we get
... (mexico production)/0.03 = (world production)
The change in world production is the difference between the amounts for the two years, so is
... (production increase) = (2007 world production) - (2000 world production)
... = 24/0.03 - 18/0.03 = (24 - 18)/0.03
... = 6/0.03 = 200 . . . . million metric tons
The appropriate choice is (D) 200.