What does d=18in mean

What is the common difference for this arithmetic sequence? -6,-2,2,6,10 a.4 b.5 c.3 d.6

Ben and cam are scuba diving. ben is 15.815.8 meters below the surface of the water. cam is 4.24.2 meters above ben. what is cam's position relative to the surface of the water? choose 1 choose 1 (choice a) a 11.611.6 meters above the surface of the water (choice b) b 11.611.6 meters below the surface of the water (choice c) c 2020 meters above the surface of the water (choice d) d 20 meters below the surface of the water

You have z baseball cards. christopher has 12 fewer baseball cards than you do. which expression correctly shows how many baseball cards christopher has?