What does it mean to find the reciprocal?

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

The square root of 9x plus 7 plus the square rot of 2x equall to 7

Runner ran 1 4/5 miles on monday and 6 3/10 on tuesday. how many times her monday’s distance was her tuesdays distance