Is the function between height in centimeters and height in inches an example of direct variation, inverse variation or neither? Please answer I am desperate

Which of the following is most likely the next step in the series? a3z, b6y, c9x, d12w, е15v, f18u

Colby and jaquan are growing bacteria in an experiment in a laboratory. colby starts with 50 bacteria in his culture and the number of bacteria doubles every 2 hours. jaquan starts with 80 of a different type of bacteria that doubles every 3 hours. let x equal number of days. colbys experiment follows the model: a.) y=50*2^x b.) y=50*2^8x c.) y=50*2^12x jaquans experiment follows the model: a.)80*2^x b.)80*2^8x c.)80*2^12x

Apositive number a or the same number a increased by 50% and then decreased by 50% of the result?