An airplane takes off, climbs 3,000 ft, and then descends 600 ft. What is the airplane's current height? what's the numerical expression ?

Is a positive integer raised to a negative power always positive

Acertain volume of water contains 100000 hydrogen atoms and 50,000 oxygen atoms how many hydrogen atoms are in a volume of water containing 4 million oxygen atoms

In a small section of a stadium there are 40 spectators watching a game between the cook islands and fiji. they all support at least one of the two teams. 25 spectators support the cook islands and 16 of these support both teams. how many support only fiji?