How do I find the midsegment?

Asequence of numbers begins with 12 and progresses geometrically. each number is the previous number divided by 2. which value can be used as the common ratio in an explicit formula that represents the sequence? 1/2 2 6 12

Tickets to a science exposition cost $5.75 each for studentd and $7.00 for adults. how many students and adults went if the ticket charge was $42.75

How many 3-digit numbers can you write using only digits 1 and 7? (of course, digits can repeat.) how many 3-digit numbers can you write using only digits 1 and 7? (of course, digits can repeat.)