The elements found in greatest abundance in the Earth include oxygen, silicon, aluminum, iron and calcium; these substances also make up the bulk of the moon. Although the moon is a<span>n airless world, it has large amounts of oxygen in the form of solid chemical compounds.</span>
Replace the x in 7x by (3x + 1):-
(f o g)(x) = 7 * (3x + 1)
= 21x + 7 which is choice D.
I believe the answer is 150 miles, with a cost of $60
